Coronary artery spasm induced by trigeminal nerve stimulation and vagal reflex during intracranial operation.

This report describes a case of ventricular fibrillation resulting from coronary vasospasm during intracranial operation under general anesthesia. An autonomic response associated with the intracranial procedure caused a coronary spasm, which was worsened by alpha-agonists. Nitroglycerin effectively resolved the coronary spasm and co-complications persisted.     

A rare complication of trigeminal nerve stimulation during radiofrequency thermocoagulation: sudden ST segment elevation.

Coronary vasospasm resulting from a sudden autonomic response associated with an intracranial procedure was encountered during percutaneous radiofrequency trigeminal rhizotomy. Although it is very rare, careful monitoring and readiness for the occurrence of such a potentially lethal situation with necessary medications may prevent a fatal outcome.     

Neurinomas of the trigeminal nerve.

Neurinomas of the trigeminal nerve are rare tumours. Six cases of a series of 8,894 intracranial tumours operated upon in the Neurosurgical Clinic of Bucharest are reported. The literature is reviewed. One hundred one other cases have been found. The signs and symptoms produced by these tumours, their slow development, the radiological and other diagnostic findings, the treatment and the prognosis are discussed.     

Electrophysiological mapping of the trigeminal nerve root during microvascular decompression for trigeminal neuralgia

A method for intraoperative electrophysiological mapping of the intracranial root of the trigeminal nerve was studied in five patients with trigeminal neuralgia. During surgery, the trigeminal nerve root was stimulated centrally with a bipolar electrode, and antidromic responses were recorded peripherally from three branches of the trigeminal nerve in the face. In all patients, the fibers of the individual subdivisions of the trigeminal nerve root were successfully localized based on the peripheral sites of antidromic response. This neural mapping was used during microvascular decompression in four patients and during a rhizotomy procedure in one patient. As a result of mapping, the fibers of the trigeminal division subserving the pain were clearly confirmed to be compressed by the artery in all four patients who were undergoing microvascular decompression. Likewise, the antidromic responses precisely identified the first division of the trigeminal nerve, which should be preserved to avoid postoperative corneal ulcers in patients undergoing rhizotomy. Based on these findings, it was concluded that this technique enables surgeons to precisely identify which fibers of the trigeminal nerve root should be decompressed or divided during surgery for trigeminal neuralgia.     

Diagnostic relevance of trigeminal evoked potentials following infraorbital nerve stimulation

A new tool in neurophysiological exploration of the trigeminal nerve has recently been introduced. It has been demonstrated that stimulation of the infraorbital nerve trunk gives rise to very reliable scalp responses reflecting the activity of the afferent pathway between the maximally nerve and the brain stem. The authors demonstrate that alterations of such trigeminal evoked responses fit with documented pathological processes at various locations along the trigeminal pathway (maxillary sinus, parasellar region, and within the brain-stem parenchyma). They report the findings in 68 patients suffering from "idiopathic" trigeminal neuralgia. Alterations of the response were detected in 33 cases, suggesting that some damage of the nerve had taken place either at the root entry zone into the pons (23 cases) or slightly distal to it (10 cases). Such results support the hypothesis that trigeminal neuralgia may be due to a compression of the trigeminal root at the pons entry zone.     

Endoscope-assisted microvascular decompression of the trigeminal nerve.

Twenty-one patients with classic symptoms of trigeminal neuralgia underwent microvascular decompression of the trigeminal nerve through a retrosigmoid approach to the cerebellopontine angle. Endoscopy was used as an adjunctive imaging modality to microscopy. Specifically, endoscopes were used to confirm nerve-vessel conflicts identified by the microscope and to reveal others that escaped microscopic survey. Endoscopes were also used to assess the adequacy of the decompression performed microscopically. A total of 51 nerve-vessel conflicts were identified and treated, 14 of which were discovered only after endoscopy. Additionally, in 5 patients endoscopic examination of the surgical intervention demonstrated that further maneuvers were required to completely decompress the nerve. These results highlight the value of endoscopy in the diagnosis and therapy of cranial nerve pathology in the posterior fossa.     

Monitoring of immobility to noxious stimulation during sevoflurane anesthesia using the spinal H-reflex

BACKGROUND: The spinal H-reflex has been shown to correlate with surgical immobility, i.e., the absence of motor responses to noxious stimulation, during isoflurane anesthesia. Here, the authors established individual concentration-response functions for H-reflex amplitude and tested the predictive power of the H-reflex for movement responses during sevoflurane anesthesia in comparison to electroencephalographic parameters. In addition, they investigated the effect of noxious stimulation on the H-reflex itself. METHODS: The authors studied 12 female patients during sevoflurane anesthesia before surgery. The sevoflurane concentration was increased, a laryngeal mask was inserted, and then the sevoflurane concentration was decreased until H-reflex amplitude (recorded over the soleus muscle) recovered. Thereafter, the end-tidal sevoflurane concentration was kept at a constant value close to the minimum alveolar concentration for suppression of movement responses after tetanic stimulation (MACtetanus), determined by the Dixon up-down method. Pharmacodynamic modeling of H-reflex amplitude and of the Bispectral Index was performed, and predictive values for motor responses to noxious electrical stimulation (50 Hz, 60 mA tetanus, volar forearm) were compared using the prediction probability. RESULTS: Concentration-dependent depression of H-reflex amplitude by sevoflurane was well modeled (median r2 = 0.97) by a sigmoid function with a median EC50 of 1.5 vol% and a median slope parameter of 3.7, much steeper than the slope for the Bispectral Index. MACtetanus calculated by logistic regression was 1.6 vol%. H-reflex amplitude predicted motor responses to noxious stimulation with a prediction probability of 0.76, whereas the prediction probability for Bispectral Index and spectral edge frequency (SEF95) were not different from chance alone. Noxious stimulation was followed by a substantial increase of H-reflex amplitude for several minutes, whereas the Bispectral Index and SEF95 exhibited no significant changes. CONCLUSIONS: Suppression of movement to noxious stimulation and suppression of H-reflex amplitude by sevoflurane follow similar concentration-response functions. Although this does not imply a causal relation, it explains the high predictive value of H-reflex amplitude for motor responses to noxious stimuli, even in a narrow concentration range around the MACtetanus.     

Neurinomas of the trigeminal nerve

Neurinomas of the trigeminal nerve are rare. Based on an analysis of the published cases and on six additional cases of our own classification into three types is proposed: Type I: neurinoma of the roots in the posterior fossa, Type II: neurinoma of the Gasserian ganglion, Type III: neurinoma of the trigeminal branches. This classification allows a better adaptation of the surgical procedure to the individual case. The trigeminal nerve originates from a sensory root and a motor root which emerge from the pons and gain the middle cranial fossa floor over the apex of the petrousrigde before forming the Gasserian ganglion. The three branches of the trigeminal nerve originate at the Gasserian ganglion. Neurinomas of this nerve are relatively rare, as there are only 183 published cases. A study of the literature reveals that their incidence among brain tumours is from 0.2 to 0.4% according to the authors. Based on the published material and six personal cases and also on the anatomical, clinical and neuroradiological findings three major types of neurinomas of the trigeminal nerve can be distinguished according to their origin: neurinomas developed in the posterior fossa (type I) on the nerve roots, neurinomas of the Gasserian ganglion (type II) developed in the temporal fossa and neurinomas of the branches of the trigeminal nerve (type III). Transitional forms between the various types are possible and express special conditions of development. Each of these topographical forms has a specific clinical and radiological picture and each requires specific surgical treatment. This will be demonstrated by analysing our own six cases and the cases reported in the literature.     

Neurilemomas of the trigeminal nerve

Sixteen patients with trigeminal neurilemoma have been treated at the University Health Center of Pittsburgh during the last 15 years. Two patients had middle fossa tumors arising from the trigeminal ganglion, four had posterior fossa tumors arising from the trigeminal roots, six had "hourglass" lesions extending above and below the tentorium and involving the trigeminal ganglion and its roots, and four had tumors arising from the trigeminal branches and extending through the superior orbital fissure, foramen rotundum, or foramen ovale. In seven patients, tumor had also invaded the cavernous sinus. The clinical and radiographic features of these tumors, the operative approaches employed, and the postoperative outcome are discussed. Complete tumor excision was achieved in 12 patients; all 12 remain free of recurrence 3 to 157 months after surgery. In contrast, all four patients who underwent subtotal tumor excision showed progressive neurological deterioration from regrowth of residual tumor within 3 years of the initial surgery. Two of these four subsequently had total tumor excision and both are disease-free 23 and 34 months after the second procedure. Major morbidity developed in only one of the 16 patients. There were no operative deaths. Nine patients had preserved or improved trigeminal function after treatment.     

Arterial cross compression of the trigeminal nerve at the pons in trigeminal neuralgia. Case report with autopsy findings.

The autopsy findings in a patient with trigeminal neuralgia who died from unrelated causes are presented. Arterial cross compression of the appropriate trigeminal nerve at the pons was demonstrated. The relationship of arterial cross compression to trigeminal neuralgia is briefly discussed.     

Avulsion of the peripheral nerve of the trigeminal nerve

There are variety of surgical methods in treating trigeminal neuralgia. They can all be devided in two large groups: less invasive procedures and decopmressive procedures in the region of pontocerebelar angle. Peripheral neurectomy, exeresis or avulsion of peripheral branches of trigeminal nerv are methods for elderly patients with serious cardiopulmonal disturbances. We performed avulsion of peripheral branches at 58 patients, all older than 60 years. In 32 patients we did avulsion of only one of three branches of trigeminal nerv, while in 26 patients the combined avulsion of two branches was performed. There were no postoperative complications.     

Fully endoscopic vascular decompression of the trigeminal nerve.

Microvascular decompression of the trigeminal nerve is an accepted and effective means of treating patients with trigeminal neuralgia in whom compression of the nerve by a vascular structure is implicated in the pathogenesis of the disease. The current standard technique uses the binocular operating microscope for all intra-operative visualization. Posterior fossa endoscopy has demonstrated that the endoscope provides more comprehensive views of the anatomy of the cerebellopontine angle than does the operating microscope. To date, endoscopy has only been used to supplement microscopy in cranial nerve decompression surgery. In this report, we describe our completely endoscopic surgical technique as we present the case of a patient with trigeminal neuralgia who underwent successful vascular decompression by this approach. Using this technique the offending vessel was separated from the nerve with minimal brain retraction or dissection of surrounding structures. This report represents the first documented case where the endoscope was used as the exclusive imaging modality for decompression of the trigeminal nerve. From our experience we conclude that the endoscope's superior visualization more accurately identifies neurovascular conflicts, and provides a comprehensive evaluation of the completeness of the decompression. Additionally, this new method minimizes the risks of brain retraction and extensive dissection often required for microscopic exposure. From this study we conclude that completely endoscopic vascular decompression represents the next step forward in the safe and effective surgical treatment of trigeminal neuralgia.     

Intrinsic arteriovenous malformation embedded in the trigeminal nerve of a patient with trigeminal neuralgia

A 66-year-old man presented with typical right trigeminal neuralgia. Neuroimaging showed a small arteriovenous malformation (AVM) in the right cerebellopontine angle. Suboccipital craniotomy verified that the AVM was almost completely embedded in the root entry zone of the trigeminal nerve and the nerve axis was tilted infero-posteriorly. The patient obtained complete pain relief without sequelae after surgery by transposition of the superior cerebellar artery and correction of the tilted nerve axis. The nidus of the unresected AVM was obliterated by gamma knife radiosurgery.