Remote peritentorial hemorrhage complicating supratentorial aneurysmal surgery: a report of three cases and literature review

We herein coin the term “remote peritentorial hemorrhage (RPTH)” and present three cases with “RPTH” after supratentorial aneurysmal surgeries, including two with remote cerebellar hemorrhage (RCH) and one with remote temporobasal hemorrhage. The RCH may result from rupture of the superior cerebellar veins due to excessive cerebrospinal fluid (CSF) loss. The mechanism behind the remote temporobasal hemorrhage may be similar to that of RCH. It can be explained by tearing of the temporobasal veins as a result of brain shift owing to intracranial hypotension stemming from intensive loss of CSF. As far as we know, this is the first report of such a bleeding pattern of probable venous origin. The results of this study could shed light on the “RPTH” physiopathology.     

Remote cerebellar haemorrhage after lumbar spine surgery: case report

Remote cerebellar haemorrhage (RCH) is a well-described complication of supratentorial surgical procedures with an incidence ranging between 0.2 and 4.9 %, but is a rare complication of spinal surgery. We report a case of RCH in a 65-year-old woman who showed sudden mental deterioration 48 h after lumbar spinal surgery, which was complicated by incidental dural tearing with minimal CSF loss. Brain CT scan revealed hypodense areas compatible with acute infarction involving mostly the left cerebellar hemisphere. No cerebral bleeding was observed. MRI was also performed revealing small cerebellar areas of acute infarction mainly relating the vermis and the left postero-inferior cerebellar hemisphere with haemorrhagic transformation and mass effect in the posterior fossa producing acute hydrocephalus. Haematoma removal was initially attempted by means of a suboccipital craniotomy. An external ventricular derivation was placed in a second procedure 24 h later due to the persistence of ventricular dilatation. At discharge the patient was only showing a slight dysmetria with the fine motor skills of hands and fingers. All cases of RCH after spinal surgery reported in the literature are invariably associated to iatrogenic dural tearing; although CSF loss seems to play the key role in the pathogenesis of this rare complication, the exact pathophysiology of this condition still remains undetermined.     

Remote cerebellar hemorrhage after supratentorial procedures (part 1): a systematic review

A remote cerebellar hemorrhage (RCH) is a spontaneous bleeding in the posterior fossa, which may rarely occurs as a complication of supratentorial procedures, and it shows a typical bleeding pattern defined “the zebra sign.” However, its pathophysiology still remains unknown. We performed a comprehensive review collecting all cases of RCH after supratentorial craniotomies reported in literature in order to identify the most frequently associated procedures and the possible risk factors. We assessed percentages of incidence and 95 % confidence intervals of all demographic, neuroradiological, and clinical features of the patients. Univariate and multivariate analyses were used to evaluate their association with outcome. We included 49 articles reporting 209 patients with a mean age of 49.09?±?17.07 years and a male/female ratio 130/77. A RCH was more frequently reported as a complication of supratentorial craniotomies for intracranial aneurysms, tumors debulking, and lobectomies. In the majority of cases, RCH occurrence was associated with impairment of consciousness, although some patients remained asymptomatic or showed only slight cerebellar signs. Coagulation disorders, perioperative cerebrospinal fluid drainage, hypertension, and seizures were the most frequently reported risk factors. Zebra sign was the most common bleeding pattern, being observed in about 65 % out of the cases, followed by parenchymal hematoma and mixed hemorrhage in similar percentages. A multivariate analysis showed that symptomatic onset and intake of antiplatelets/anticoagulants within a week from surgery were independent predictors of poor outcome. However, about 75 % out of patients showed a good outcome and a RCH often appeared as a benign and self-limiting condition, which usually did not require surgical treatment, but only prolonged clinical surveillance, unless in the event of the occurrence of complications.     

Remote cerebellar hemorrhage after spinal procedures (part 2): a systematic review

A remote cerebellar hemorrhage (RCH) is a spontaneous bleeding in the posterior fossa, which can be rarely observed as a complication of spine surgery. As well as for RCH reported after supratentorial procedures, it shows a characteristic bleeding pattern defined “zebra sign”. Nowadays, RCH pathophysiology still remains unknown. We performed a comprehensive review, collecting all cases of RCH after spine surgery reported in literature in order to identify the procedures most frequently associated with RCH and the possible risk factors. We assessed percentages of incidence and 95 % confidence interval of all demographic, neuroradiological, and clinical features. Univariate and multivariate analyses were used to evaluate their association with outcome. We included 44 articles reporting 57 patients with mean age of 57.6?±?13.9 years and a male/female ratio of 23/34. A RCH was more frequently reported as a complication of decompressive procedures for spinal canal stenosis, particularly when associated with instrumented fusion, followed by spinal tumor debulking and disc herniation removal. In the majority of cases, RCH occurrence was characterized by progressive impairment of consciousness, whereas some patients complained non-specific symptoms. Coagulation disorders, hypertension, and placement of postoperative subfascial drainages were the most frequently reported risk factors. The occurrence of intraoperative dural lesions was described in about 93 % of patients. Zebra sign was the most common bleeding pattern (about 43 % of cases) followed by parenchymal hematoma (37.5 %) and mixed hemorrhage (about 20 %). Impairment of consciousness at clinical onset and intake of anticoagulants/antiplatelets appeared associated with poor outcome at univariate analysis. However, more than 75 % of patients showed a good outcome and a RCH often appeared as a benign and self-limiting condition, which usually did not require surgical treatment, but only prolonged clinical surveillance, unless of the occurrence of complications.     

Remote cerebellar hemorrhage after supratentorial surgery

OBJECTIVE: Remote cerebellar hemorrhage (RCH) is an infrequent and poorly understood complication of supratentorial neurosurgical procedures. We retrospectively compared 42 patients who experienced RCH with a case-matched control cohort, to delineate risk factors associated with the occurrence of this complication. METHODS: Between 1988 and 2000, 42 patients experienced RCH after supratentorial neurosurgical procedures at our institution. Diagnoses were made on the basis of postoperative computed tomographic or magnetic resonance imaging findings in all cases. The medical records for these patients were reviewed and compared with those for a control cohort of 43 patients, matched for age, sex, surgical lesion, and type of craniotomy, who were treated during the same period. RESULTS: RCH most commonly occurred after frontotemporal craniotomies for unruptured aneurysm repair or temporal lobectomy and was frequently an incidental finding on postoperative computed tomographic scans. However, some cases of RCH were associated with significant morbidity, and two patients died. Preoperative aspirin use and elevated intraoperative systolic blood pressure were significantly associated with RCH (P = 0.026 and P = 0.036, respectively). Pathological findings for two cases demonstrated hemorrhagic infarctions in both. CONCLUSION: RCH most commonly follows supratentorial neurosurgical procedures, performed with the patient in the supine position, that involve opening of cerebrospinal fluid cisterns or the ventricular system (such as unruptured aneurysm repair or temporal lobectomy). Preoperative aspirin use and moderately elevated intraoperative systolic blood pressure are potentially modifiable risk factors associated with the development of RCH. Although RCH can cause death or major morbidity, most cases are asymptomatic or exhibit a benign course. Cerebellar "sag" as a result of cerebrospinal fluid hypovolemia, causing transient occlusion of superior bridging veins within the posterior fossa and consequent hemorrhagic venous infarction, is the most likely pathophysiological cause of RCH.     

Infratentorial hemorrhage following supratentorial surgery]

Hemorrhage in regions remote from the site of initial intracranial operations is rare, but does occur. We report three cases of cerebellar hemorrhage that developed after supratentorial surgery, all of which had similar clinical findings and CT images. The first case was a 37-year-old man with a craniopharyngioma in the suprasellar lesion. Partial removal of the tumor was performed through frontal craniotomy and the translaminaterminals approach. A large quantity of cerebospinal fluid (CSF) was suctioned from the third ventricle during the operation, resulting in marked brain shrinkage. The second and third cases were 34- and 51-year-old women with unruptured right middle cerebral aneurysms. Clipping of the aneurysms through the pterional approach was performed in both cases. In the second case, CSF was suctioned in large quantity from the carotid and prechiasmal cistern at the operation, resulting in marked brain shrinkage. In the third case, however, only a small volume of CSF was suctioned from the carotid and prechiasmal cistern during the operation, and no marked brain shrinkage was observed. CT scan showed that the hematomas were located mainly in the subdural or the subarachnoid spaces over the cerebellar hemisphere and partially extending into the cerebellar cortex. The mechanism of cerebellar hemorrhage in these series of patients was thought to be multifactorial. The possible etiology for cerebellar hemorrhage in the three cases presented was examined, including the role of CSF suction during surgery and disturbance of venous circulation in the posterior fossa. Suction of the CSF may cause intracranial hypotension. Further reduction of intracranial pressure leads to an increased transluminal venous pressure. There was no episode of hypertension or disturbed blood coagulation during or after the operation. The preoperative angiogram also revealed no abnormality at the region of the posterior fossa. Neuroimaging of infratentorial hemorrhage after supratentorial craniotomy is obviously different from that of hypertensive cerebellar hemorrhage. From the shape or extension of the hemorrhage, the main vessels of hemorrhage are the superior vermian vein and their tributaries damaged by stretching and tearing of these vessels. These vessels are not demonstrable in the angiogram, therefore there is no evidence for this hypothesis and the etiology is still unclear. There is no doubt, however, that there was a disturbance of venous circulation in this complication. We would like to emphasize the possibility of this complication. Patients who show signs of difficulty in awaking from anesthesia or the development of new neurological deficits not attributed to direct operative procedure after supratentorial craniotomy must be evaluated early, with adequate imaging including the posterior fossa.     

Cerebellar hemorrhage after supratentorial craniotomy

BACKGROUND: Cerebellar hemorrhage following supratentorial craniotomy is a very seldom described but serious complication. The present study evaluates the significance of presurgical and surgical factors that may predispose patients to these bleeding episodes. METHODS: The data of 52 cases of cerebellar hemorrhage following supratentorial craniotomy, 9 from our records and 43 from the literature, were analyzed with regard to various variables. RESULTS: The findings suggest that this clinical picture is unrelated to age, previous arterial hypertension, inherent or induced coagulopathies, type of primary underlying lesion, intraoperative positioning of the patient, type of anesthesia, or intracranial hypotension and its sequels. It entails significant morbidity, with one third of the patients left with cerebellar dysfunction or in a dependent state, and carries a mortality of about 25%. CONCLUSION: Not one single presurgical or surgical factor can reliably predict the occurrence of cerebellar hemorrhage after supratentorial craniotomy, and the etiology of this entity still remains unclear. The most important keys to minimize the hazardous sequelae are to be aware of this potential complication and to diagnose it early.     

Remote cerebellar hemorrhage as an early and potentially lethal complication of a discal lumbar herniation surgery

Remote cerebellar hemorrhage (RCH) is an infrequent but serious complication after lumbar herniation surgery. Little is known about this complication but excessive cerebrospinal fluid (CSF) leakage is thought to be a leading cause of RCH. We describe the case of a patient suffering from a life-threatening RCH, which occurred a few hours after lumbar disc herniation surgery.     

Remote cerebellar hemorrhage after foramen magnum decompression surgery for Chiari I malformation--case report

A 47-year-old woman underwent decompressive suboccipital craniectomy and C1 laminectomy with duroplasty in the prone position for Chiari malformation type I and syringomyelia. The arachnoid membrane was not injured. Intraoperative echography showed good enlargement of the subarachnoid space. No closed subcutaneous drain was used. The patient complained of repeated nausea and vomiting 3 hours after the operation, and computed tomography revealed remote cerebellar hemorrhage on postoperative day 1. The cerebellar hemorrhage was treated conservatively, and the symptoms continued only for 3 days after surgery. Dural opening with rapid loss of cerebrospinal fluid (CSF) has occurred in every reported case of remote cerebellar hemorrhage complicating intracranial and spinal procedures. Loss of CSF is the main pathogenesis of this condition. In our case, the most probable pathomechanism seems to involve stretching of the infratentorial cerebellar bridging veins due to cerebellar sagging because of dural opening in the prone position and drop in CSF pressure. Such a complication is rare but should be considered after foramen magnum decompression surgery if the patient shows unusual symptoms of repeated vomiting.     

Cerebellar hemorrhage arising postoperatively as a complication of supratentorial surgery: a retrospective study

OBJECT: Postoperative cerebellar hemorrhage as a complication of supratentorial surgery is an increasingly recognized clinical entity. So far, it has remained unclear whether this complication constitutes an intraoperative or postoperative event. The observation of such cases prompted the authors to analyze retrospectively their series of supratentorial craniotomies. The aim of this study was to determine the incidence of cerebellar hemorrhage and its temporal relationship to supratentorial surgery. METHODS: The authors reviewed discharge notes and reports on postoperative computerized tomography (CT) scans for 1650 patients who had undergone supratentorial craniotomy between January 1998 and February 2001. The retrospective study led to the identification of 10 patients who had sustained cerebellar hemorrhage as a complication of supratentorial surgery. Because it was routine to perform CT scanning following craniotomy, an early CT scan obtained within the 1st postoperative hour (mean 24 minutes after wound closure) was available in eight of the 10 patients. In seven of these patients no hemorrhage was found immediately after surgery, and in only one patient was there the suspicion of cerebellar hemorrhage. In the whole series of 10 patients, cerebellar hemorrhage was detected during the later postoperative course, after a mean interval of 7 hours and 35 minutes (range 1 hour and 49 minutes-144 hours) following surgery. The incidence of cerebellar hemorrhage was 0.6% of all patients who underwent supratentorial surgery. Among patients suffering from epilepsy the incidence was 4.6%, and in those patients who underwent temporal lobe resection it was 12.9%. CONCLUSIONS: The authors have demonstrated that cerebellar hemorrhage as a complication of supratentorial surgery arises not as an intraoperative event, but as a postoperative event. Resective nontumorous temporal lobe procedures place patients at particular risk for this complication. Evidence suggests that the complication might be precipitated by postoperative suction drainage.     

Cerebellar hemorrhage after spinal surgery: report of two cases and literature review

OBJECTIVE AND IMPORTANCE: Cerebellar hemorrhage remote from the site of surgery may complicate neurosurgical procedures. We describe our experience with two cases of cerebellar hemorrhage after spinal surgery and review the three cases previously reported in the literature to determine whether these cases provide insight regarding the pathogenesis of remote cerebellar hemorrhage. CLINICAL PRESENTATION: One of our patients developed cerebellar hemorrhage in the vermis and right hemisphere after transpedicular removal of a partially intradural T9-T10 herniated disc with the patient in the prone position. The other patient developed cerebellar hemorrhage in the vermis and bilateral hemispheres after L3-S1 decompression and instrumentation with the patient in the prone position, during which the dura was inadvertently opened. INTERVENTION: The first patient was treated conservatively and had mild residual dysarthria and gait ataxia 2 months after surgery. The second patient underwent exploration and revision of the lumbar wound with primary dural repair. The cerebellar hemorrhage was treated conservatively, and the patient had mild dysarthria and ataxia 1 month after surgery. CONCLUSION: Cerebellar hemorrhage must be considered in patients with unexplained neurological deterioration after spinal surgery. Dural opening with loss of cerebrospinal fluid has occurred in every reported case of cerebellar hemorrhage complicating a spinal procedure, supporting the hypothesis that loss of cerebrospinal fluid is central to the pathogenesis of this condition. Because remote cerebellar hemorrhage can occur after procedures with the patient in the supine, sitting, and prone positions, patient positioning seems unlikely to play a causative role in its occurrence.     

Cerebellar hemorrhage after supratentorial surgery for treatment of epilepsy: report of three cases.

OBJECTIVE AND IMPORTANCE: We report three cases of cerebellar hemorrhage complicating supratentorial craniotomies for the treatment of epilepsy. In a literature review, we identified only four similar cases of cerebellar hemorrhage after temporal lobectomy for the treatment of epilepsy. CLINICAL PRESENTATION AND RESULTS: Three young and otherwise healthy patients underwent frontal, occipital, and temporal resections for the treatment of refractory epilepsy. The hemorrhage manifested as peduncular tremor, ataxia, and decerebrate posturing presenting early in the postoperative period. The diagnosis was established by computed tomography and/or magnetic resonance imaging. Benign outcomes were observed for all patients. CONCLUSION: Based on the available data, it is our opinion that brain dislocation resulting from excessive intraoperative cerebrospinal fluid drainage is a possible mechanism for this rare complication of supratentorial craniotomy. The overdrainage seems to be less hazardous when the procedure is performed for the removal of space-occupying mass lesions. In contrast, the resection of nonexpanding tissues, such as in lobectomies for the treatment of epilepsy, may be an additional risk factor, because the incidence of this complication seems to be higher in these situations.     

Hemorragia intraventricular como complicación tras una cirugía espinal. Caso clínico

Remote intracranial hemorrhage (ICH) is a rare but dreaded complication after spinal surgery. The physiopathology of this phenomenon is closely related to a loss of cerebrospinal fluid (CSF) after an incidental durotomy during spine surgery. The most common remote ICH location is cerebellar, but few articles report intraventricular hemorrhage. Its clinic is associated with cerebral hypotension due to decreased CSF, mainly headache, dysarthria, hemiparesis, an impaired level of awareness and seizures.The diagnosis of remote ICH after a non-cranial surgery can be a challenge to anesthesiologists, this pathology should be suspected face an immediate neurological deterioration after anesthetic awakening. Non-specific symptoms make it difficult to identify the origin of intracranial hemorrhagic from other differential diagnoses.We present a patient with an impaired level of awareness and seizures who suffered a hemorrhage in the right ventricle with cerebral and cerebellar edema in the immediate postoperative period after spinal surgery.     

Intracranial hemorrhage following lumbar spine surgery

Background

Intracranial hemorrhage is a serious but rare complication of spinal surgery, which can occur in the intracerebral, cerebellar, epidural, or subdural compartment.

Purpose

To describe patients with intracranial hemorrhage after lumbar spinal surgery and present clinical and diagnostic imaging findings.

Methods

In this retrospective study, medical records of 1,077 patients who underwent lumbar spinal surgery in our tertiary referral neurosurgery center between January 2003 and September 2010 were studied. The original presentations of the patients before the surgical intervention were herniated lumbar disc, spinal canal stenosis, spondylolisthesis, lumbar spinal trauma, and lumbar spine and epidural tumor. The operations performed consisted of discectomy, multiple level laminectomy, stabilization and fusion, lumbar instrumentation, and lumbar spinal and epidural tumor resection.

Results

Four cases developed intracranial hemorrhage including acute subdural hematoma (one case), epidural hematoma (one case), and remote cerebellar hemorrhage (two cases). The clinical and diagnostic imaging characteristics along with treatments performed and outcomes of these four patients are described and the pertinent literature regarding post-lumbar spinal surgery intracranial hemorrhages is reviewed.

Conclusion

Though rare, intracranial hemorrhage can occur following lumbar spinal surgery. This complication may be asymptomatic or manifest with intense headache at early stages any time during the first week after surgery. Dural tear, bloody CSF leakage, focal neurologic symptoms, and headache are indicators of potential intracranial hemorrhage, which should be considered during or following surgery and necessitate diagnostic imaging.     

Cerebellar hemorrhage after spinal surgery: case report and review of the literature

Recent reports indicate that cerebellar hemorrhage after spinal surgery is infrequent, but it is an important and preventable problem. This type of bleeding is thought to occur secondary to venous infarction, but the exact pathogenetic mechanisms are unknown. This report details the case of a 48-year-old woman who developed remote cerebellar hemorrhage after spinal surgery. The patient presented with a herniated lumbar disc, spinal stenosis, and spondylolisthesis, and underwent multiple-level laminectomy, discectomy, and transpedicular fixation. The dura mater was opened accidentally during the operation. There were no neurologic deficits in the early postoperative period; however, 12 h postsurgery the patient complained of headache. This became more severe, and developed progressive dysarthria and vomiting as well. Computed tomography demonstrated small sites of remote cerebellar hemorrhage in both cerebellar hemispheres. The patient was treated medically, and was discharged in good condition. At 6 months after surgery, she was neurologically normal. The case is discussed in relation to the ten previous cases of remote cerebellar hemorrhage documented in the literature. The only possible etiological factors identified in the reported case were opening of the dura and large-volume cerebrospinal fluid loss.     

Bilateral Late Remote Cerebellar Hemorrhage as a Complication of a Lumbo-Peritoneal Shunt Applied After Spinal Arteriovenous Malformation Surgery

Abstract

Background/Objective: Cerebellar hemorrhage is a very infrequent and unpredictable complication of spinal surgery. To the best of our knowledge, cerebellar hemorrhage resulting from the insertion of a lumbo-peritoneal shunt through which cerebrospinal fluid (CSF) is slowly drained has not been documented to date.

Methods: Case report.

Results: A 47-year-old woman presented with lower extremity weakness. Spinal arteriovenous malformation was diagnosed, and she underwent surgery. Her neurologic status improved; however, CSF collected subcutaneously as a cyst and leaked 21 days after surgery. The patient underwent urgent surgery during which the durai defect was repaired and a lumbo-peritoneal catheter was put in place to treat the CSF leakage. The lumbo-peritoneal drainage system was removed when bilateral cerebellar hemorrhage was seen 12 days later. Physical therapy was stopped, and conservative treatment was initiated consisting of bed rest, analgesics, sedatives, and careful monitoring of blood pressure. The patient's headache gradually resolved; physical therapy was restarted to rehabilitate this patient with paraparesis.

Conclusions: Remote cerebellar hemorrhage seems to be life threatening and entails significant morbidity. Cerebellar symptoms, and even a late sudden headache after spinal surgery, may be signs of remote cerebellar hemorrhage, which is a rare complication.

J Spinal Cord Med. February 2010; 33(1): 77–79     

Cerebellar haemorrhage as a complication after supratentorial craniotomy

Summary Four cases are presented, in whom cerebellar haemorrhages appeared as a complication following supratentorial craniotomy for a giant aneurysm, for tumours in three cases. Two patients died. Intracranial hypotension in combination with disturbed blood coagulation is discussed as possible pathogenesis. Because this seems to be a rare complication-similar cases have not yet been described in the literature-its timely diagnosis may be missed.     

Remote cerebellar haemorrhage after placement of an external ventricular drainage for acute hydrocephalus: A case report

Introduction

Remote cerebellar haemorrhage (RCH) is a rare complication following a craniotomy. This generally benign phenomenon is an identifiable complication of supratentorial craniotomies and should not be mistaken with other pathologies. The most common presenting symptom is a decrease in the level of consciousness but in some cases the RCH may be asymptomatic and accidentally discovered in follow-up CT scans.

Remote medulla ablongata ventral acute subarachnoid hemorrhage following cervical spinal surgery: A case report

IntroductionThe incidence of remote intracranial hemorrhage (RICH) in patients during spinal surgery is rare and the detailed mechanism remains unclear.Presentation of caseA 55-year-old man had undergone cervical discectomy and fusion at C5–6 and C6–7 due to herniated disc and secondary spinal canal stenosis. He had severe headache 20 h postoperatively and his drain output increased from 100 to 350 mL in the second 10 h after surgery. Computed tomography (CT) and magnetic resonance imaging (MRI) were performed and he was diagnosed with acute subarachnoid hemorrhage in the ventral medulla oblongata. The drainage tube was quickly removed. Infusion of hypertonic saline was used to reduce intracranial pressure and nimodipine prevented vasospasm around the brainstem. The patient made a gradual, satisfactory recovery with conservative treatment.DiscussionThe most likely pathomechanism leading to RICH is venous bleeding due to rapid leak of a large amount of cerebral spinal fluid (CSF) after spinal surgery. If the patient has a headache or neurological complaints after spinal surgery, immediate imaging is recommended to confirm the diagnosis. Treatment depends on the amount and location of intracranial hemorrhage.ConclusionRICH is a serious but rare complication of spinal surgery and cerebellar hemorrhage is the most common. The most important pathomechanism leading to RICH after spinal surgery is venous bleeding due to rapid leak of a large amount of CSF. Timely CT is necessary to exclude RICH. Treatment of RICH depends on the size of the intracranial hematoma and the patient’s symptoms.     

Compression of the internal jugular vein by the transverse process of the atlas as the cause of cerebellar hemorrhage after supratentorial craniotomy.

BACKGROUND: The cerebellar hemorrhage reported in numerous cases after supratentorial craniotomy has uniformly exhibited the characteristics of hemorrhage associated with venous infarction rather than arterial bleeding. The cause has remained obscure, although previous reports suggested that the cause may be obstruction of flow in the internal jugular vein immediately below the base of the skull. METHODS: The microsurgical anatomy of 36 internal jugular veins in the upper cervical region were defined in adult cadaveric specimens using 3-40x magnification with special attention to the relationship of the vein to the atlas. RESULTS: In every specimen, the posterior wall of the internal jugular vein rested against the transverse process of the atlas as the vein descended immediately below the jugular foramen. In 14 of 36 specimens, the transverse process indented the posterior wall of the vein, causing the vein to be slightly or moderately angulated as it descended across the anterior surface of the transverse process. Three veins were severely kinked as they descended across the transverse process of the atlas. CONCLUSIONS: Obstruction of flow in the internal jugular vein at the site where the vein descends across the transverse process of the atlas is a likely cause of the venous hypertension that has resulted in the cerebellar hemorrhage reported in numerous cases after supratentorial craniotomy. An examination of the biomechanics of the region confirms that turning the head to the side opposite a supratentorial craniotomy and extending the neck, common practices with unilateral supratentorial craniotomy, further aggravates the angulation and obstruction of the internal jugular vein at the transverse process of C1 on the side ipsilateral to the craniotomy.