Microvascular decompression for trigeminal neuralgia: update.

PURPOSE OF REVIEW: A recent Cochrane systematic review of surgical interventions for trigeminal neuralgia found not a single trial of what is becoming the most popular surgical intervention, namely microvascular decompression (MVD). With an increasing number of anticonvulsant drugs it is likely that patients may not be offered a surgical option for management of their trigeminal neuralgia for many years. RECENT FINDINGS: Current studies repeat much of what is already in the literature but there is an increasing appreciation of the value of preoperative imaging and the need to be more precise with the diagnosis. The search for prognosticators for good outcomes continues to dominate the literature. SUMMARY: Microvascular decompression in correctly diagnosed patients is probably the most effective therapy. However, high-quality prospective studies of MVD in a population that has been well phenotyped and which is assessed pre and postoperatively using psychometrically tested questions, administered at regular intervals by independent observers, are needed to provide clear evidence of its superiority over medical therapies.

Radiofrequency thermocoagulation for trigeminal neuralgia without intra-operative patient waking.

OBJECTIVE: It is proposed that radiofrequency thermocoagulation (RFT) under general anaesthesia without waking the patient intra-operatively, which is usually performed to confirm lesion location, will reduce the peri-operative discomfort and anxiety suffered by patients. METHODS: A retrospective review of all procedures, identified through standard hospital audit codes and performed by a single surgeon from 2000 to 2007. Postal questionnaires were sent to all eligible patients. Outcome criteria included pain relief, adverse events and patients' views on satisfaction, timing and outcomes. A Kaplan-Meier plot was used to determine actuarial rates of pain relief. RESULTS: Follow-up was available for 84% (37/44) of patients. Complete post-operative pain relief was 96% (42/44). The actuarial rates of complete pain relief at 6, 12, 24 and 36 months were 89%, 79%, 66% and 43%. No patients reported an outcome that did not meet their expectations while 71% (20/28) had an outcome that was better than their expectation. Serious complications included corneal numbness affecting 12% (5/41), but no cases of keratitis and a single case of anaesthesia dolorosa. CONCLUSIONS: Not waking a patient intra-operatively when performing a RFT is a viable treatment option that results in excellent early pain relief, comparable to results in the literature and without an increase in complications. Patient reported outcomes indicate a high rate of satisfaction and are a novel addition to our understanding of the procedure; there is no comparable data in the literature documenting patient satisfaction outcomes when the procedure is performed with patient waking.

Clinicopathological review of patients with and without multiple sclerosis treated by partial sensory rhizotomy for medically refractory trigeminal neuralgia: a 12-year retrospective study.

BACKGROUND: Trigeminal nerve root entry zone demyelination has been implicated as a cause of trigeminal neuralgia (TN) in multiple sclerosis (MS) and patients with nerve root vascular compression. We have examined the relationship between pathology and treatment outcome in patients with and without MS, treated for intractable TN by partial sensory rhizotomy (PSR). METHODS: We reviewed the operative records, electron microscopic biopsy findings and post-operative satisfaction and pain scores of 23 MS and 47 non-MS patients who underwent PSR between 1992 and 2004. RESULTS: The MS and non-MS patients had similar ages of onset of TN, duration of symptoms, age at surgery and proportions with typical and atypical symptoms. Demyelination was present in 16 MS and 23 non-MS patients (p=0.129), and a compressing vessel in 5 MS and 23 non-MS patients (p=0.039). Of those with demyelination, vascular compression was documented in 3 MS and 15 non-MS patients (p=0.008). Pain and satisfaction scores were similar in both groups. Recurrent TN was more commonly associated with a compressing vessel (p=0.019). CONCLUSIONS: TN is frequently associated with nerve root entry zone demyelination in MS and patients with nerve root vascular compression. The characteristics of the TN and response to PSR are similar in both groups. Persistent vascular compression increases the risk of recurrent TN after PSR.

Preliminary evaluation of a novel intraparenchymal capacitive intracranial pressure monitor.

OBJECT: Intracranial pressure (ICP) monitors are currently based on fluid-filled, strain gauge, or fiberoptic technology. Capacitive sensors have minimal zero drift and energy requirements, allowing long-term implantation and telemetric interrogation; their application to neurosurgery has only occasionally been reported. The aim of this study was to undertake a preliminary in vitro and in vivo evaluation of a capacitive telemetric implantable ICP monitor. METHODS: Four devices were tested in air- and saline-filled pressure chambers; long-term capacitance-pressure curves were obtained. Devices implanted in a gel phantom and in a piglet were placed in a 3-T MR unit to evaluate MR compatibility. Four devices were implanted in a piglet neonatal hydrocephalus model; output was compared with ICP obtained through fluid-filled transduction and a strain-gauge ICP monitor. RESULTS: The capacitance-pressure relationship was constant over 4 weeks, suggesting minimal zero drift during this period. There were no temperature changes around the monitor. Signal loss at the sensor was minimal in both the phantom and the piglet. Over 114,000 measurements were obtained; the difference between mean capacitive ICP and fluid-transduced ICP was 1.8 ± 1.42 mm Hg. The correlation between ICP from the capacitive sensor and fluid-filled transducer (r = 0.97, p < 0.0001) or strain-gauge monitor (r = 0.99, p < 0.0001) was excellent. In vivo monitoring was restricted to 48 hours due to problems with robustness in the clinical environment. CONCLUSIONS: This preliminary study demonstrates minimal long-term zero drift in vitro, good MR compatibility, and good correlation with other methods of ICP monitoring in vivo in the short term. Further long-term in vivo study is required.

Neuralgia of the glossopharyngeal and vagal nerves: long-term outcome following surgical treatment and literature review.

This study describes our experience in the surgical treatment of neuralgia of the glossopharyngeal and vagal nerves. Over the last 19 years, 21 patients underwent surgery. Their case notes were reviewed to obtain demographic information, clinical presentation, surgical findings and early results. All patients were then contacted by telephone for long-term results and complications. Independent analysis of results was carried out by a Neurology team. Ten patients had microvascular decompression (MVD). Four patients had MVD and nerve section. In the remaining seven patients, the glossopharyngeal and first two rootlets of the vagal nerve were sectioned. Nineteen (90%) of 21 patients experienced complete relief of pain immediately after surgery. The remaining patients reported an improvement in their symptoms. There were no mortalities. Four patients experienced short-term complications, which resolved. Two patients were left with a persistent hoarse voice. At follow-up (mean duration of 4 years), there was no recurrence in symptoms. In our experience, surgery is safe and effective for the treatment of vago-glossopharyngeal neuralgia.

Memory loss resulting from fornix and septal damage: impaired supra-span recall but preserved recognition over a 24-hour delay.

Despite increasing evidence that the fornix is important for memory, uncertainty remains about the exact nature of subsequent impairments arising from damage to this tract. This uncertainty is often created by pathology in additional brain structures. The present study involved a young man, DN, who had almost complete bilateral loss of the rostral columns of the fornix and much of the surrounding septum in the left hemisphere following the surgical removal of a cavernous angioma. Quantitative MRI analyses of structure size, normalized to intracranial volume, showed no difference in any of the additional brain regions measured, apart from those areas removed to expose the tumor. DN showed a marked, stable anterograde memory impairment that was still present 4 years postsurgery. In contrast, DN performed within normal levels on most tests of recognition memory. This sparing was most striking when given a 24-hr delay between study and test of the Warrington Recognition Memory Test. This recall/recognition dissociation provides further evidence for neuroanatomical divisions within recognition memory processes.

Management of petrous endostosis in posterior fossa procedures for trigeminal neuralgia.

OBJECTIVE: Within a series of 440 consecutive patients who underwent posterior fossa procedures for trigeminal neuralgia (TN), the site of neurovascular conflict was obscured by petrous endostosis in 15 patients. The surgical management and clinical outcomes of these patients are presented. METHODS: We retrospectively analyzed the prospectively collected data of all patients with a diagnosis of TN from 1980 to 2005. Clinical presentation, preoperative imaging, intraoperative findings, surgical technique, and outcomes were recorded. A postal follow-up questionnaire and a visual analog scale of 100 points were used for outcome assessment and patient satisfaction. RESULTS: All 15 patients presented with typical TN, had preoperative imaging suggestive of vascular compression of the trigeminal nerve root, and underwent standard retromastoid craniotomy. The juxta-petrous portion of the trigeminal nerve root was obscured by petrous endostosis. The neurovascular conflict was revealed and dealt with after drilling of the endostosis in 11 patients, and four patients had endoscopic-assisted exploration of the region of the endostosis. A pontotrigeminal vein caused compression in most cases. Three patients had endoscopic-assisted division of the vein. All patients had immediate relief of pain and were 100% satisfied with the results of surgery after a mean follow-up period of 38.6 months. Four patients developed a cerebrospinal fluid leak, and five patients experienced postoperative headaches. CONCLUSION: Petrous endostosis is an uncommon finding in posterior fossa procedures for TN (3.4%). However, it can obscure the region of neurovascular conflict, which is venous compression in these cases. We have found that drilling away endostosis or using endoscopic-assisted microsurgery increases the chances of good outcome and avoids unnecessary rhizotomy. All magnetic resonance imaging scans should be inspected for evidence of petrous endostosis and, when present, a bone window computed tomographic scan should be performed to clarify the image and check for the presence of petrous air cells. If the endostosis is drilled, failure to detect and to seal these air cells thoroughly can result in postoperative cerebrospinal fluid rhinorrhea. Attention to these details will optimize the surgical results. However, the use of an angled endoscope avoids this problem and is now our preferred method.

Hemifacial spasm caused by pontine glioma: case report and review of the literature.

Hemifacial spasm (HFS) is an involuntary paroxysmal contractions of the facial musculature, caused generally by vascular compression of the seventh cranial nerve at its root exit zone from the brain stem. The case of an adult man harbouring brain stem glioma (BSG) whose only neurological signs were left HFS and mild facial weakness is reported. Radiological and neurophysiological findings are described. No responsible vessel could be identified during surgery, but the causative lesion was found to be an astrocytic tumour encasing the facial nerve at its root exit zone from the brain stem. The rarity of such a condition prompted us to review the literature. Nine cases, including our patient presenting with HFS caused by BSG, are reviewed.

Patient reports of satisfaction after microvascular decompression and partial sensory rhizotomy for trigeminal neuralgia.

OBJECTIVE: There are no reports of patient satisfaction surveys after either a microvascular decompression (MVD) or a partial sensory rhizotomy (PSR) for trigeminal neuralgia. This study compares patient satisfaction after these two types of posterior fossa surgery for trigeminal neuralgia, because it is postulated that recurrences, complications, and previous surgical experience reduce satisfaction. METHODS: All patients who had undergone their first posterior fossa surgery at one center were sent a self-complete questionnaire by an independent physician. Among the 44 questions on four standardized questionnaires were 5 questions that related to patient satisfaction and experience of obtaining care. Patients were divided into those having their first surgical procedure (primary) and those who had had previous ablative surgery (nonprimary). RESULTS: Response rates were 90% (220 of 245) of MVD and 88% (53 of 60) of PSR patients. Groups were comparable with respect to age, sex, duration of symptoms, mean duration of follow-up, and recurrence rates. Overall satisfaction with their current situation was 89% in MVD and 72% in PSR patients. Unsatisfied with the outcome were 4% of MVD and 20% of PSR patients, and this is a significant difference (P < 0.01). Satisfaction with outcome was higher in those undergoing this as a primary procedure. In the primary group, satisfaction was dependent on recurrence and complication/side effects status (each P < 0.01), but this was not the case in the nonprimary group. Patients expressed a desire for earlier posterior fossa surgery in 73% of MVD and 58% of PSR patients, and this was highest in the primary group. The final outcome was considered to be better than expected in 80% of MVD and 54% of PSR patients, but 22% of the PSR group (P < 0.01) thought they were worse off. CONCLUSION: Patients undergoing posterior fossa surgery as a primary procedure are most satisfied and PSR patients are least satisfied, partly because of a higher rate of side effects.

Trigeminal neuralgia caused by microarteriovenous malformations of the trigeminal nerve root entry zone: symptomatic relief following complete excision of the lesion with nerve root preservation.

OBJECT: Within a series of 341 consecutive patients who underwent posterior fossa surgery for trigeminal neuralgia (TN), in five the cause was found to be a microarteriovenous malformation (micro-AVM) located in the region of the trigeminal nerve root entry zone (REZ). The surgical management and clinical outcomes of these cases are presented. METHODS: Patients were identified from a prospectively collected database of all cases of TN treated at one institution between 1980 and 2000. Presentation was clinically indistinguishable from TN caused by vascular compression. Preoperative imaging, including computerized tomography scanning (two cases) and magnetic resonance (MR) imaging and MR angiography (three cases), failed to demonstrate an AVM except for one case in which multiple abnormal vessels were identified in the trigeminal REZ on an MR image obtained using a 1.5-tesla magnet. All patients underwent a standard retromastoid craniotomy. In all cases a small AVM embedded in the trigeminal REZ was identified and completely excised, with preservation of the trigeminal nerve. All patients experienced immediate relief of pain following surgery. Postoperatively, in one patient a small pontine hematoma developed, resulting in permanent trigeminal nerve anesthesia in the V2 and V3 divisions. All patients were free from pain at a mean follow-up period of 30 months. CONCLUSIONS: These rare lesions are usually angiographically occult, but may sometimes be identifiable on high-resolution MR images. Total microsurgical resection with nerve preservation is possible, although operative complications are relatively common, reflecting the intimate association between these lesions and the pons. Complete resection is advised not only for symptom relief, but also to eliminate the theoretical risk of pontine hemorrhage.