Microvascular decompression of the root emerging zone for hemifacial spasm: evaluation by fusion magnetic resonance imaging and technical considerations

Object

The root exit zone (RExZ) of the facial nerve has been considered to be the target in microvascular decompression (MVD) for hemifacial spasm. However, more proximal segments with oligodendrocyte-derived myelin, where the facial nerve root emerges at the pontomedullary sulcus and adheres to the brainstem surface (root emerging zone [REmZ]), may also be susceptible to neurovascular compression. This study evaluated the predictive value of magnetic resonance (MR) imaging in detecting and assessing the features of vascular compression, especially in the pontomedullary sulcus, and describes the technical considerations of MVD procedures for the more proximal segments of the facial nerve.

Methods

Twenty patients treated with MVD underwent three-dimensional constructive interference in steady-state MR imaging and three-dimensional time-of-flight MR angiography. Their fusion images were used to evaluate the anatomical neurovascular relationships and intraoperative findings were analyzed.

Results

Most offending arteries at the REmZ and the RExZ of the facial nerve were correctly identified by fusion MR imaging. During surgery, neurovascular contacts were identified at one or more segments of the facial nerve in all patients. The REmZ of the facial nerve was affected in 55 % of the patients. The most common offending vessel at the REmZ was the posterior inferior cerebellar artery rather than the anterior inferior cerebellar artery. The key procedure to explore the deep-seated REmZ in the pontomedullary sulcus was full dissection of the lower cranial nerves to the brainstem origin.

Conclusions

Our definition more correctly describes the specific anatomical relationship of the facial nerve origin from the brainstem and the clinically relevant target for MVD surgery. Fusion MR imaging is very useful to identify neurovascular contacts at both the RExZ and the REmZ of the facial nerve.     

Role of postoperative magnetic resonance imaging after microvascular decompression of the facial nerve for the treatment of hemifacial spasm

OBJECTIVE: This study was performed to investigate the role of postoperative three-dimensional short-range magnetic resonance angiography in the prediction of clinical outcomes after microvascular decompression (MVD) for the treatment of hemifacial spasm. METHODS: We examined pre- and postoperative magnetic resonance imaging scans obtained between March 1999 and May 2000 for 122 patients with hemifacial spasm, to evaluate the degree of detachment of the vascular contact and changes in the positions of offending vessels. The degree of vascular decompression of the facial nerve root was classified into three groups, i.e., contact, partial decompression, or complete decompression. Contact was defined as unresolved compression, as indicated by postoperative three-dimensional short-range magnetic resonance angiography. Partial decompression was defined as incompletely resolved compression; vascular indentation of the facial nerve was improved, but contact with the facial nerve remained. Complete decompression was defined as completely resolved compression. These findings were compared with the surgical findings and clinical outcomes. RESULTS: Of 122 patients with MVD, complete decompression of offending vessels at the root entry zone of the facial nerve was observed for 106 patients (86.9%), partial decompression was observed for 10 patients (8.2%), and contact with offending vessels was observed for 6 patients (4.9%) by using postoperative three-dimensional short-range magnetic resonance angiography. Our study demonstrated that the types of offending vessels affected neither the degree of decompression of the root entry zone of the facial nerve nor surgical outcomes (P > 0.05). Also, there was no significant relationship between the degree of decompression and improvement of symptoms (P > 0.05). Furthermore, there was no significant relationship between the degree of decompression and the timing of symptomatic improvement (P > 0.05). CONCLUSION: Our data suggest that MVD of the facial nerve alone may not be sufficient to resolve symptoms for all patients with hemifacial spasm. Therefore, unknown factors in addition to vascular compression may cause symptoms in certain cases, and it may be necessary to remove those factors, simultaneously with MVD, to obtain symptom resolution.     

Classification of neurovascular compression in typical hemifacial spasm: three-dimensional visualization of the facial and the vestibulocochlear nerves

OBJECT: In this paper, the authors introduce a method of noninvasive anatomical analysis of the facial nerve-vestibulocochlear nerve complex and the depiction of the variable vascular relationships by using 3D volume visualization. With this technique, a detailed spatial representation of the facial and vestibulocochlear nerves was obtained. Patients with hemifacial spasm (HFS) resulting from neurovascular compression (NVC) were examined. METHODS: A total of 25 patients (13 males and 12 females) with HFS underwent 3D visualization using magnetic resonance (MR) imaging with 3D constructive interference in a steady state (CISS). Each data set was segmented and visualized with respect to the individual neurovascular relationships by direct volume rendering. Segmentation and visualization of the facial and vestibulocochlear nerves were performed with reference to their root exit zone (REZ), as well as proximal and distal segments including corresponding blood vessels. The 3D visualizations were interactively compared with the intraoperative situation during microvascular decompression (MVD) to verify the results with the observed microneurosurgical anatomy. RESULTS: Of the 25 patients, 20 underwent MVD (80%). Microvascular details were recorded on the affected and unaffected sides. On the affected sides, the anterior inferior cerebellar artery (AICA) was the most common causative vessel. The posterior inferior cerebellar artery, vertebral artery, internal auditory artery, and veins at the REZ of the facial nerve (the seventh cranial nerve) were also found to cause vascular contacts to the REZ of the facial nerve. In addition to this, the authors identified three distinct types of NVC within the REZ of the facial nerve at the affected sides. The authors analyzed the varying courses of the vessels on the unaffected sides. There were no bilateral clinical symptoms of HFS and no bilateral vascular compression of the REZ of the facial nerve. The authors discovered that the AICA is the most common vessel that interferes with the proximal and distal portions of the facial nerve without any contact between vessels and the REZ of the facial nerve on the unaffected sides. CONCLUSIONS: Three-dimensional visualization by direct volume rendering of 3D CISS MR imaging data offers the opportunity of noninvasive exploration and anatomical categorization of the facial nerve-vestibulocochlear nerve complex. Furthermore, it proves to be advantageous in establishing the diagnosis and guiding neurosurgical procedures by representing original MR imaging patient data in a 3D fashion. This modality provides an excellent overview of the entire neurovascular relationship of the cerebellopontine angle in each case.     

Microvascular decompression for spasmodic torticollis

Summary Twenty patients with spasmodic torticollis (ST) were treated by microvascular decompression (MVD) of the spinal accessory nerves, the upper cervical nerve roots and the brainstem. Thirteen were female and seven male. Median age was 47 years (range 39 to 70 years). Median duration of symptoms was 5 years (range 4 months to 17 years). Ten had right horizontal; nine, left horizontal; and one, retrocollis ST. Twenty-two operations were performed on twenty patients, suboccipital craniectomy and C₁ laminectomy in 18 and retromastoid craniectomy in 4 operations.The most common compressing blood vessels were the vertebral artery and/or the posterior inferior cerebellar artery. No nerve section was performed. Three patients died of unrelated conditions, 3, 5 1/2, and 6 years postoperatively, respectively. Minimum follow-up period in the rest of the cases is 5 years (range 5 to 10 years). Thirteen (65%) were cured, four (20%) improved with minimal spasm, one (5%) improved with moderate spasm, and two (10%) improved minimally or unchanged. In most cases the cure or improvement was noticed gradually over 6 months to two years following the operation.There was no operative mortality. Postoperative morbidities included transient cerebrospinal fluid leakage through the surgical incision in one case and an apparent multiple small vessel stroke involving periventricular white matter in one reoperation case with full recovery.MVD for ST is a nondestructive benign procedure with high probability of cure or significant improvement.     

Imaging of hemifacial spasm

Almost all primary hemifacial spasms are associated with one or more neurovascular conflicts, most often at the root exit zone in the immediate vicinity of the brainstem. Imaging has first to exclude a secondary hemifacial spasm and secondly to search for and characterize the responsible neurovascular conflict(s). Magnetic resonance imaging should include high-resolution anatomical hyper T2-weighted sequences and magnetic resonance angiography by using 1.5 or even better 3 Tesla magnets. The most frequent vascular compressions are from the anterior-inferior cerebellar artery, the posterior-inferior cerebellar artery and the vertebrobasilar artery; venous conflicts are very rare. Conflicts are often multiple; also, the same vessel may compress the facial nerve in two places. Also, conflicts may be aided by particular anatomical circumstances, including arterial dolichoectasia, posterior fossa with a small volume or bony malformations.     

Indications and Timings of Re-operation for Residual or Recurrent Hemifacial Spasm after Microvascular Decompression: Personal Experience and Literature Review

We reviewed reports about the postoperative course of hemifacial spasm (HFS) after microvascular decompression (MVD), including in our own patients, and investigated treatment for delayed resolution or recurrence of HFS. Symptoms of HFS disappear after surgery in many patients, but spasm persists postoperatively in about 10–40%. Residual spasm also gradually decreases, with rates of 1–13% at 1 year postoperatively. However, because delayed resolution is uncommon after 1 year postoperatively, the following is advised: (1) In patients with residual spasms after 1 year postoperatively (incomplete cure) or who again experience spasm ≥ 1 year postoperatively (recurrence), re-operation is recommended if the spasms are worse than before MVD. (2) When re-operation is considered, preoperative magnetic resonance imaging (MRI) findings and intraoperative videos should be reviewed to ensure that no compression due to a small artery or vein was missed, and to confirm that adhesions with the prosthesis are not causing compression. If any suspicious findings are identified, the cause must be eliminated. Moreover, because of the risk of nerve injury, decompression of the distal portion of the facial nerve should be performed only in patients in whom distal compression is strongly suspected to be the cause of symptoms. (3) Cure rates after re-operation are high, but complications such as hearing impairment and facial weakness have been reported in 10–20% of cases, so surgery must be performed with great care.     

Microsurgical vascular decompression for hemifacial spasm. Follow-up over one year, clinical results and prognostic factors. Study of a series of 100 cases

BACKGROUND AND PURPOSE: The results of a series of 100 patients operated on for hemifacial spasm (HFS), using microsurgical vascular decompression (MVD), are reported. METHOD: MVD was performed through a retromastoid keyhole approach, under monitoring of brainstem auditory evoked potentials (BAEP) and facial EMG, and consisted in dissection of VII nerve from conflicting vessel(s), and interposition of Teflon fibers and/or screen(s). RESULTS: The offending vessels found were: the antero-inferior cerebellar artery in 57 cases, the postero-inferior cerebellar artery in 56 cases, the vertebrobasilar artery in 22 cases. A multiple conflict was found in 32 cases (32%). The result was considered excellent if there was no residual spasm, good if only "minimal twitching" remained with relief>80%, poor for spasm relief 20 to 80%, and as a failure if relief<20%. The effect of MVD was satisfying (excellent or good) in 75 patients (75%) at discharge (10th day) and in 85 (85%) after 1 to 18 years follow-up (mean: 5 years). Amongst the latter patients, 29 (34%) experienced a delayed (up to 3(1/2) years in one) cure. Spasm recurrence was noted in 9 cases after satisfying effect on discharge. We encountered following permanent neurological complications: 1 facial palsy, 7 cases of hearing deficit (5 of them complete), and 1 case of IX-X deficit. Neither death nor ischaemic complication at brainstem or cerebellum. Most of our hearing complications occurred before using intraoperative BAEP monitoring (3 cases of cophosis among our first 7 patients vs 2 out of our last 93). Local complications were: 1 meningitis, 8 cases of CSF leakage requiring either a series of lumbar punctures or a lumbar external drain, and 3 cases of wound infection and/or delayed woundhealing requiring surgical treatment. CONCLUSIONS: Our data are consistent with those of the literature, especially concerning high rate of long-term success and low complication rate of MVD for HFS. We do not recommend early re-operation in case of initial poor result. Again, the necessity of intraoperative BAEP monitoring to prevent hearing morbidity is highlighted.     

Neurovascular compression findings in hemifacial spasm

OBJECT: It is generally accepted that hemifacial spasm (HFS) is caused by pulsatile vascular compression upon the facial nerve root exit zone. This 2-3 mm area, considered synonymous with the Obersteiner-Redlich zone, is a transition zone (TZ) between central and peripheral axonal myelination that is situated at the nerve's detachment from the pons. Further proximally, however, the facial nerve is exposed on the pontine surface and emerges from the pontomedullary sulcus. The incidence and significance of neurovascular compression upon these different segments of the facial nerve in patients with HFS has not been previously reported. METHODS: The nature of neurovascular compression was determined in 115 consecutive patients undergoing their first microvascular decompression (MVD) for HFS. The location of neurovascular compression was categorized to 1 of 4 anatomical portions of the facial nerve: RExP = root exit point; AS = attached segment; RDP = root detachment point that corresponds to the TZ; and CP = distal cisternal portion. The severity of compression was defined as follows: mild = contact without indentation of nerve; moderate = indentation; and severe = deviation of the nerve course. Success in alleviating HFS was documented by telephone interview conducted at least 24 months following MVD surgery. RESULTS: Neurovascular compression was found in all patients, and the main culprit was the anterior inferior cerebellar artery (in 43%), posterior inferior cerebellar artery (in 31%), vertebral artery (in 23%), or a large vein (in 3%). Multiple compressing vessels were found in 38% of cases. The primary culprit location was at RExP in 10%, AS in 64%, RDP in 22%, and CP in 3%. The severity of compression was mild in 27%, moderate in 61%, and severe in 12%. Failure to alleviate HFS occurred in 9 cases, and was not related to compression location, severity, or vessel type. CONCLUSIONS: The authors observed that culprit neurovascular compression was present in all cases of HFS, but situated at the RDP or Obersteiner-Redlich zone in only one-quarter of cases and rarely on the more distal facial nerve root. Since the majority of culprit compression was found more proximally on the pontine surface or even pontomedullary sulcus origin of the facial nerve, these areas must be effectively visualized to achieve consistent success in performing MVD for HFS.     

Reappearance of Cranial Nerve Dysfunction Symptoms Caused by New Artery Compression More than 20 Years after Initially Successful Microvascular Decompression: Report of Two Cases

Reappearance of symptoms of cranial nerve dysfunction is not uncommon after successful microvascular decompression (MVD). The purpose of this study was to report two quite unusual cases of recurrent and newly developed hemifacial spasm (HFS) caused by a new conflicting artery more than 20 years after the first successful surgery. In Case 1, the first MVD was performed for HFS caused by the posterior inferior cerebellar artery (PICA) when the patient was 38 years old. After 26 symptom-free years, HFS recurred on the same side of the face due to compression by the newly developed offending AICA. In Case 2, the patient was first operated on for trigeminal neuralgia by transposition of the AICA at 49 years old, but 20 symptom-free years after the first MVD, a new offending PICA compressed the facial nerve on the same side, causing HFS. These two patients underwent reoperation and gained satisfactory results postoperatively. Reappearance of symptoms related to compression of the root exit zone (REZ) by a new offending artery after such a long symptom-free interval since the first effective MVD is rare. Here, we describe two such unusual cases and discuss how to manage and prevent such reappearance of symptoms after a long time interval.     

A growing aneurysm of the posterior inferior cerebellar artery complicated with cerebellar infarction: A case report

Introduction and importanceHereby we describe an instructive patient with cerebellar infarction and a growing aneurysm at the posterior inferior cerebellar artery (PICA), which was not a true cause of infarction.Case presentationA 50-year-old female presented with dizziness and posterior neck pain at our hospital (Mitaka city, Tokyo, Japan). Diffusion weighted magnetic resonance (MR) images showed cerebellar infarction in the left PICA territory and MR angiography study showed an aneurysm at the origin of the left PICA, which grew in 2 weeks. Since we considered cerebellar infarction was caused by thrombosis from the aneurysm, trapping of the PICA and occipital artery-PICA bypass was performed to prevent recurrent cerebellar infarction and rupture of the aneurysm by neurosurgeons. During the operation, dissection was observed at the distal PICA, which was diagnosed to be the true cause of cerebellar infarction. By the follow-up for 12 months at an outpatient, there was no recurrence of cerebral infarction.Clinical discussionA specimen of the artery showing the findings of dissection was not obtained, and the pathological diagnosis could not be made. It would be controversial whether a surgical procedure presented here was the most optimal.ConclusionThis is a first reported case of growing aneurysms and cerebral infarction due to arterial dissection. Even if cerebral infarction is accompanied by growing aneurysms, arterial dissection should be included in the differential diagnoses of a cause of infarction. Posterior cervical pain can be a clue for early appropriate diagnosis in such a case.     

Intraoperative monitoring of facial EMG responses during microvascular decompression for hemifacial spasm. Prognostic value for long-term outcome: a study in a 33-patient series

Lateral spread responses (LSR), an electrophysiological characteristic of hemifacial spasm (HFS), can be recorded during surgery. This work aims at evaluating the prognostic value of the persistence or suppression of the LSR at the end of the microvascular decompression (MVD) procedure of the facial nerve. Thirty-three patients with HFS, which had been evolving for 5.5 years, underwent MVD with intraoperative EMG. Monitoring required the placement of a needle in the frontalis and mentalis muscles. Responses were recorded after stimulation of inferior or superior branches of the facial nerve to search for abnormal ephaptic LSR. Preoperative abnormal LSRs were present in all patients. In 23 patients, LSR disappeared with vascular decompression and was not present upon closure. Among those patients, 20 were considered clinically cured and three still presented with mild/moderate spasm at 3-month follow-up. At late follow-up, 22 patients were free of spasm. One patient had recurrence of spasm at month 10. On the contrary, 10 patients had persistent abnormal LSR upon closure. Among those, seven were cured at early follow-up (3 months on average), whereas spasm disappeared at late follow-up (12 to 36 months) in the other three patients. The prognostic value of LSR monitoring is questionable; a good clinical result may be obtained in patients who presented with persistent LSR at the end of MVD. Delayed cure strongly supports the hypothesis that HFS is not only due to the mechanical pulsations of the elongated artery against the root exit zone of the facial nerve, but also to demyelination of the nerve and/or hyperactivity of the facial motornucleus generated by the neurovascular compression.     

Preoperative evaluation of neural tracts by use of three-dimensional anisotropy contrast imaging in a patient with brainstem cavernous angioma: technical case report

OBJECTIVE AND IMPORTANCE: We describe a case of brainstem cavernous angioma in which the neural tracts were evaluated before surgery by three-dimensional anisotropy contrast (3-DAC) magnetic resonance imaging. CLINICAL PRESENTATION: A 64-year-old man presented with a cavernous angioma located intrinsically in the brainstem and manifesting as gait ataxia. 3-DAC imaging demonstrated that the lesion was located outside the left inferior cerebellar peduncle and inside the middle cerebellar peduncle. INTERVENTION: The intact brain surface was incised, and the lesion was removed successfully on the basis of the preoperative 3-DAC images. The patient exhibited temporary exacerbation of his gait ataxia, but the symptom improved 3 months after surgery. Postoperative 3-DAC imaging demonstrated resection of the lesion and preservation of the left inferior and middle cerebellar peduncles. CONCLUSION: 3-DAC imaging may provide essential information about the neural tracts for the planning of brainstem surgery.     

Microvascular decompression for treating hemifacial spasm: lessons learned from a prospective study of 1,174 operations

The authors critically analyzed a large series of patients with hemifacial spasm (HFS) and who underwent microvascular decompression (MVD) under a prospective protocol. We describe several “lessons learned” that are required for achieving successful surgery and proper postoperative management. The purpose of this study is to report on our experience during the previous 10 years with this procedure and we also discuss various related topics. From April 1997 to June 2009, over 1,200 consecutive patients underwent MVD for HFS. Among them, 1,174 patients who underwent MVD for HFS with a minimum 1 year follow-up were enrolled in the study. The median follow-up period was 3.5 years (range, 1-9.3 years). Based on the operative and medical records, the intraoperative findings and the postoperative outcomes were obtained and then analyzed. At the 1-year follow-up examination, 1,105 (94.1%) patients of the total 1,174 patients exhibited a “cured” state, and 69 (5.9%) patients had residual spasms. In all the patients, the major postoperative complications included transient hearing loss in 31 (2.6%), permanent hearing loss in 13 (1.1%), transient facial weakness in 86 (7.3%), permanent facial weakness in 9 (0.7%), cerebrospinal fluid leak in three (0.25%) and cerebellar infarction or hemorrhage in two (0.17%). There were no operative deaths. Microvascular decompression is a very effective, safe modality of treatment for hemifacial spasm. MVD is not sophisticated surgery, but having a basic understanding of the surgical procedures is required to achieve successful surgery.     

Hemifacial spasm caused by a tortuous recurrent perforating artery: A case report

IntroductionWhen the culprit vessel in hemifacial spasm (HFS) is hard to determine, this is a challenge in microvascular decompression (MVD) surgery. In such a situation, small arteries such as perforators to the brainstem might be suspected. But small arteries are omnipresent near the facial nerve root exit/entry zone (fREZ). How to decide whether a given small artery is responsible for HFS is unclear.MethodWe report a case with a previously unreported form of neurovascular impingement, in which the culprit was found to be the recurrent perforating artery (RPA) from the anterior inferior cerebellar artery (AICA). An aberrant anatomic configuration of the RPA was found intraoperatively, which we thought was responsible for generating focal pressure on the facial nerve.Case reportA 62-year-old woman presented with a 1-year history of paroxysmal but increasingly frequent twitching in her right face. MRI showed tortuosity of the vertebral artery and apparently marked neurovascular impingement on the asymptomatic left side, while only the right AICA could be implicated as the possible culprit. Hemifacial spasm was diagnosed based on the typical clinical manifestation, and MVD was performed. The pre-meatal segment of the AICA was found not to be impinging the facial nerve at any susceptible portion near the fREZ: root exit point, attached segment, or root detachment point. The real culprit was in fact the RPA. This occult culprit vessel was tortuous, forming a coil-shaped twist which was interposed between the facial nerve and the intermediate nerve near the root detachment point. Focal pressure atrophy of the nerve was clearly observed at the compressing site. The patient achieved total spasm relief immediately after surgery, and remained spasm-free at 1-year follow-up, without any postoperative complications.ConclusionMVD is the only curative treatment for hemifacial spasm, but with a failure rate of around 10%. Mistaking the real culprit has been reported to be the most likely reason for surgical failure. Therefore, intraoperative identification of atypical occult forms of vascular compression is of importance to improve surgical outcome. In the present case, the RPA formed a coil-shaped twist, which inflicted focal vascular compression causing hemifacial spasm. We recommend careful inspection of the recurrent perforating artery during MVD for HFS, and decompressing any such neurovascular impingement.     

The natural history of hemangioblastomas of the central nervous system in patients with von Hippel-Lindau disease

OBJECT: The goals of this study were to define the natural history and growth pattern of hemangioblastomas of the central nervous system (CNS) that are associated with von Hippel-Lindau (VHL) disease and to correlate features of hemangioblastomas that are associated with the development of symptoms and the need for treatment. METHODS: The authors reviewed serial magnetic resonance images and clinical histories of 160 consecutive patients with VHL disease who harbored CNS hemangioblastomas and serially measured the volumes of tumors and associated cysts Six hundred fifty-five hemangioblastomas were identified in the cerebellum (250 tumors), brainstem (64 tumors, all of which were located in the posterior medulla oblongata), spinal cord (331 tumors, 96% of which were located in the posterior half of spinal cord), and the supratentorial brain (10 tumors). The symptoms were related to a mass effect. A serial increase in hemangioblastoma size was observed in cerebellar, brainstem, and spinal cord tumors as patients progressed from being asymptomatic to symptomatic and requiring surgery (p < 0.0001). Twenty-one (72%) of 29 symptom-producing cerebellar tumors had an associated cyst, whereas only 28 (13%) of 221 nonsymptomatic cerebellar tumors had tumor-associated cysts (p < 0.0001). Nine (75%) of 12 symptomatic brainstem tumors had associated cysts, compared with only four (8%) of 52 nonsymptomatic brainstem lesions (p < 0.0001). By the time the symptoms appeared and surgery was required, the cyst was larger than the causative tumor; cerebellar and brainstem cysts measured 34 and 19 times the size of their associated tumors at surgery, respectively. Ninety-five percent of symptom-producing spinal hemangioblastomas were associated with syringomyelia. The clinical circumstance was dynamic. Among the 88 patients who had undergone serial imaging for 6 months or longer (median 32 months), 164 (44%) of 373 hemangioblastomas and 37 (67%) of 55 tumor-associated cysts enlarged. No tumors or cysts spontaneously diminished in size. Symptomatic cerebellar and brainstem tumors grew at rates six and nine times greater, respectively, than asymptomatic tumors in the same regions. Cysts enlarged seven (cerebellum) and 15 (brainstem) times faster than the hemangioblastomas causing them. Hemangioblastomas frequently demonstrated a pattern of growth in which they would enlarge for a period of time (growth phase) and then stabilize in a period of arrested growth (quiescent phase). Of 69 patients with documented tumor growth, 18 (26%) harbored tumors with at least two growth phases. Of 160 patients with hemangioblastomas, 34 patients (median follow up 51 months) were found to have 115 new hemangioblastomas and 15 patients new tumor-associated cysts. CONCLUSION: In this study the authors define the natural history of CNS hemangioblastomas associated with VHL disease. Not only were cysts commonly associated with cerebellar, brainstem, and spinal hemangioblastomas, the pace of enlargement was much faster for cysts than for hemangioblastomas. By the time symptoms appeared, the majority of mass effect-producing symptoms derived from the cyst, rather than from the tumor causing the cyst. These tumors often have multiple periods of tumor growth separated by periods of arrested growth, and many untreated tumors may remain the same size for several years. These characteristics must be considered when determining the optimal timing of screening for individual patients and for evaluating the timing and results of treatment.     

Teflon granuloma after microvascular decompression for trigeminal neuralgia

BACKGROUND: Our purpose was to research the factors that may induce Teflon granuloma in trigeminal neuralgia patients who have undergone microvascular decompression (MVD) procedures, to propose methods for the early diagnosis of Teflon granuloma, and provide suggestions for reducing this complication. METHODS: From 1985 to 1996, 89 trigeminal neuralgia patients underwent MVD with Teflon felt to separate the offending vessels and the trigeminal nerve. Ten patients had secondary explorations for recurrent symptoms. Five patients developed recurrent facial pain associated with facial numbness within a certain period after the first operation. We reviewed the onset and site of the initial symptoms, the duration of the symptoms, the operative findings and methods, and the results of the operations. In the reoperative patients, we analyzed the initial and secondary symptoms after the first operation, and the time to relapse. We compared the operative findings and methods in these operations. RESULTS: The operative findings in the 10 patients with recurrence were Teflon granuloma in five patients, arterial loop compression in three patients, venous compression in one patient, and negative exploration in one patient. The Teflon granuloma patients all complained of facial numbness after the first MVD operation. The incidence of Teflon granuloma after MVD was 5.6% (5/89). CONCLUSION: The Teflon felt used in the MVD procedure can produce complications. It is not absolutely inert when used in MVD procedures. When it contacts the tentorium and/or dura, an inflammatory giant-cell foreign body reaction can be induced. In the future, we should search for other implants to replace the Teflon felt. However, until new materials are found, we suggest that the Teflon felt be kept away from the tentorium and dura and placed completely within the CSF cisterna. We can diagnose Teflon granuloma early with enhanced CT and/or MRI, especially in patients with new facial numbness symptoms after Teflon MVD procedures. The results of reexploration of Teflon granulomas are more satisfactory than a negative exploration or venous compression. We may be able to decrease the incidence of Teflon granuloma. We should be more aggressive in performing reexploration in these recurrent patients.     

Diagnosis of anterior inferior cerebellar artery occlusion on magnetic resonance angiography with reference to basiparallel anatomic scanning-magnetic resonance imaging

A 67-year-old woman presented with symptomatic infarction in the territory of the anterior inferior cerebellar artery manifesting as vertigo, vomiting, and right facial weakness. Basiparallel anatomic scanning (BPAS) magnetic resonance (MR) imaging combined with MR angiography demonstrated the occluded anterior inferior cerebellar artery. Common anatomic variations and limited detection of the smaller branches on MR angiography sometimes hinder evaluation of the occluded artery. BPAS-MR imaging may have a supplementary role to MR angiography in the diagnosis of cerebellar artery occlusions.     

Intra-operative monitoring of two facial muscles in hemifacial spasm surgery

BackgroundHemifacial spasm (HFS) is a chronic facial nerve disorder characterized by spontaneous muscle contractions. Microvascular decompression (MVD) is the neurosurgical treatment of choice. Intraoperative neurophysiologic monitoring (IOM) during MVD can help determine when adequate decompression is performed.MethodsMVD with IOM was performed on 16 patients with HFS that included recording the abnormal lateral spread response (LSR) in lower facial muscles, considered as neurophysiologic marker of HFS. Two lower facial muscles were monitored as opposed to a standard monitoring of a single muscle.ResultsAll patients underwent preoperative thin cut MRI confirming the presence of neurovascular conflict. Patients underwent small retrosigmoid craniotomy and MVD. In 13 cases, the LSR guided the surgeon to continue MVD until the response was unobtainable from all recorded lower facial muscles. In four of those (30%), the LSR persisted on one of the recorded muscle and prompted further exploration and decompression until complete disappearance of LSR in all recorded muscles. In two cases, the LSR disappeared after dural opening and never recurred during the procedure, therefore the completion of MVD was based on non reappearance of LSR. In one case, the LSR persisted despite apparent complete decompression of the nerve. Fourteen patients had complete relief of their symptoms after surgery, one had partial improvement and the one with persistent LSR was unchanged.ConclusionEvaluation of the LSR by monitoring of two lower facial muscles provides valuable neurosurgical guidance during MVD for HFS. This simple modification of intra-operative monitoring may improve prediction of satisfactory MVD and HFS resolution.     

The conflicting vessels in hemifacial spasm: Literature review and anatomical-surgical implications

Since several decades, it has been established that so-called primary hemifacial spasm is linked to neuro-vascular conflicts in the facial nerve, especially its root exit zone (REZ). Based on our review of the detailed publications of literature (2489 patients), together with our own series (340 patients), the responsible vessels found at surgery were: the posterior inferior cerebellar artery in 47.2%, the anterior inferior cerebellar artery in 45.9%, the vertebro-basilar artery in 17.5%, another (smaller) artery in 11.7%. Participation of veins was very diversely estimated according to series: 4.9% on average. Multiple neuro-vascular conflicts in a same individual were frequently observed, in the order of 20 to 30% according to authors, 37% in our series. Also, abnormal conformation of the posterior fossa may play a role, such as flatness of the posterior fossa or exiguity of the cerebello-pontine angle cistern. Whatever, most neurovascular conflicts are located at brainstem and/or ventrocaudally to the facial REZ, in the order of 95% of the patients. The anatomical location and conformation of the compressive vessel(s) are crucial in determining the difficulties to identify the responsible conflict(s) and to perform effective and safe decompression. Main difficulties are encountered in cases with arteriosclerotic megadolicho-vertebrobasilar artery, at brainstem, especially when PICA and/or AICA come in association, or for neurovascular conflict(s) located at the cisternal or the intrameatal portions of the facial root. Later ones can be alone or in addition to NVC at brainstem/REZ.     

Fusion imaging of three-dimensional magnetic resonance cisternograms and angiograms for the assessment of microvascular decompression in patients with hemifacial spasms

OBJECT: The precise preoperative assessment of the complex nerve-vessel relationship at the root exit zone (RExZ) of the facial nerve is important when planning microvascular decompression (MVD) in patients with hemifacial spasms. The authors have developed an imaging technique-the fusion of 3D magnetic resonance (MR) cistemography and coregistered 3D MR angiography images-that allows clear visualization of the spatial relationship between the vessels and the rootlet of the facial nerve at the brainstem. METHODS: The authors reconstructed 3D MR cisternograms and 3D MR angiograms by using a perspective volume-rendering algorithm that they applied to the volumetric data sets of the following modalities: MR cisternography (a T,-weighted 3D fast spin echo sequence) and coregistered MR angiography (a 3D time-of-flight sequence). The complex anatomical relationship between the offending vessels and the facial nerve RExZ was inspected preoperatively by examining the fusion images from various perspectives within the cerebellopontine angle cistern, within the affected facial nerve, and through the simulated surgical route. The reconstructed 3D findings of the nerve-vessel relationship were compared with the intraoperative findings. Postoperatively, the fused 3D MR imaging technique was used to confirm that microsurgical dissection and the interposed prosthesis had succeeded in maintaining the causative vessels in a position away from the RExZ. CONCLUSIONS: The fusion of 3D MR cisternograms and 3D MR angiograms may prove useful in the pre- and postoperative assessment of MVD in patients with hemifacial spasm.