Vascular compression and cranial nerve diseases

This paper offers a review of cranial nerve rhizopathies caused by vascular compression of cranial nerves in the posterior cranial fossa. We present our results of microvascular decompression for trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia caused by compression of the 5th, 7th and 9th cranial nerves, respectively. After a median observation time of 38 months, 20 of 25 patients with trigeminal neuralgia were completely free of pain, and one patient reported more than 50% pain relief. Four out of five patients treated for hemifacial spasms were completely free of spasms. Of two patients treated for glossopharyngeal neuralgia, one reported complete pain relief, whereas the other reported less than 50% pain relief. No serious complications occurred. The results of microvascular decompression reported in the literature reviewed, including results of the treatment of tinnitus and positional vertigo due to compression of the 8th cranial nerve, hypertension due to compression of the 10th cranial nerve and spastic torticollis due to compression of the 11th cranial nerve. It is concluded that the rationale behind microvascular decompression is supported by an extensive amount of data.     

Middle fossa decompression of the trigeminal sensory root for trigeminal neuralgia--a re-appraisal and a modification of the technique

Twenty-three patients with intractable trigeminal neuralgia were treated by a modified technique of middle fossa extradural decompression of the trigeminal sensory root at the petrous ridge. After exposing the ganglion and the root at the petrous ridge, by an extradural Frazier's approach a thin layer of autogenous fat was interposed between the dura propria and the middle fossa dura anteriorly, and between the petrous ridge and the root posteriorly. The fat layers were used to prevent dural adhesions and to maintain a space between the petrous ridge and the root. The dura propria was preserved intact. All patients obtained immediate relief of pain following surgery. Twenty patients continue to remain pain free. Two patients have mild occasional pains and one has a persistent pain of moderate intensity. One patient developed a dense sensory loss and two had delayed facial weakness which recovered completely within a month. The mechanism of trigeminal neuralgia is discussed on the basis of anatomical, histopathological and electrophysiological findings and the rationale of middle fossa decompression of the root is stressed. This method is short, simple and safe and may serve as an alternative to the more recent methods of treating trigeminal neuralgia.     

The characteristics of a natural attenuated isolate of Francisella tularensis

Multimodal evoked potentials in patients with trigeminal neuralgia are analyzed in the paper. The comprehensive studies of cortical trigeminal somatosensory evoked potentials, visual evoked potentials, and brainstem auditory evoked potentials have revealed their changes that are indicative of the impaired central mechanisms of afferentation in patients with trigeminal abnormality. The findings are discussed in the light of the theory of generator mechanisms of neuropathological pain syndromes.     

Neurosurgical treatment of trigeminal neuralgia. A comparative study of alcohol block, neurectomy and electrocoagulation

The objective was to assess the present condition of patients previously treated with neurosurgical procedures for trigeminal neuralgia (TN). Between 1976 and 1991, 383 patients were treated for TN at the Department of Neurosurgery, Hvidovre Hospital. The latest surgical intervention performed was radiofrequency coagulation (64%), neurectomy (18%), alcohol block (16%), trigeminal tractotomy (1%), and microvascular decompression (1%). Questionnaires were sent to 316 patients treated neurosurgically for trigeminal neuralgia during the 16 year period. After radiofrequency coagulation, neurectomy and alcohol block, 83, 51 and 42% respectively experienced a pain free postoperative period. At present 49, 17 and 18% were without pain and 33, 21 and 36% had less pain compared with the preoperative state. Sequelae were described in 65, 57 and 49% of the patients. The four most common sequelae were hypaesthesia, paraesthesia, eye complaints, and dysaesthesia. If relevant pharmacotherapy has been tried without benefit, radiofrequency coagulation may still be considered as a treatment of trigeminal neuralgia.     

Partial sensory rhizotomy as an alternative treatment of trigeminal neuralgia

Microvascular decompression is a well established technique in the treatment of medically refractory trigeminal neuralgia when a significant vascular contact is identified during posterior fossa exploration. However, in patients with recurrent trigeminal neuralgia after this type of surgery or if no significant vascular indentation is found during surgery, a partial sensory rhizotomy is often the preferred alternative mode of treatment. For eight such patients, partial sensory trigeminal rhizotomy was performed with the involved distribution. Two patients were cases of previous failure, while the other six cases showed a lack of vascular indentation during operation. All the patient underwent microvascular decompression in addition to partial sensory trigeminal rhizotomy with dissector disruption. Sensory examination was performed during the outpatient department follow-up. In these eight such patients, five had excellent results, two continued to have mild pain that was well controlled with carbamazepine, and one had poor results. The mean follow-up period was 58 months. Our study indicates that sensory loss is compatible with the extent of nerve section and that touch loss is less evidence than sensory loss. Partial sensory trigeminal rhizotomy is recommended as the alternative treatment strategy of choice for patients with trigeminal neuralgia who lack significant vascular contact during operation.     

Microvascular decompression in the treatment of essential trigeminal neuralgia

INTRODUCTION AND OBJECTIVE: We pretend to evaluate the surgical procedure and clinical results of microvascular decompression (MVD) of 21 patients suffering from essential trigeminal neuralgia between 1989 and 1997. PATIENTS AND METHODS: Selection criteria included: ineffectiveness of pharmacological treatment, good general condition, more than five years life expectancy, and do not have undergone ablative-lesive surgical procedures before. RESULTS: After a post-surgical follow-up of between three months and three years, it was obtained a 100% success rate of immediate pain relief, with only a 14.2% recurrence. There were no sequels as those typically found in lesive techniques as paresthesias and dysesthesias, painful and/or corneal anaesthesia and motor disorders. There were no deaths, although there were three cases of post-surgical complications. CONCLUSIONS: To evaluate the long-term results of different surgical techniques in the treatment of the essential trigeminal neuralgia is outstanding the patients satisfaction rate, which not only depends on pain relief and absence of recurrence, but also and very specially on the neurological deficiencies following the procedure. So, we consider that MVD is the most effective technique both in symptoms relief and neural functions and structures preservation, even though the possibility of appearance of complications following any major surgery.     

The assessment of residual effects of a single dose of diazepam on visually-defined EEG patterns

Patients with medically intractable trigeminal neuralgia characterized by paroxysmal, triggered, trigeminally distributed pain are excellent candidates for neurosurgical intervention, which can not only relieve the pain of trigeminal neuralgia, but also eliminate the unpleasant side effects of medicines used to treat it. The two major neurosurgical choices are percutaneous denervation and microvascular decompression (MVD). Percutaneous denervation is done best when the surgeon has available radiofrequency and glycerol and uses one, the other, or both depending on technical circumstances that pertain to each patient. The percutaneous denervation is less likely than MVD to cause death, stroke, facial weakness, or hearing loss, but more likely to be associated with recurrence or dysesthesias. Patients with multiple sclerosis, medical illness, or who are elderly are much better candidates for percutaneous denervation. For any patient, a number of other factors also must be considered before deciding on a particular procedure. These include response to previous interventions, ability to tolerate carbamazepine, risk tolerance for various complications, preference regarding duration of hospital stay and postoperative recovery, presence of pain outside the trigeminal distribution, and findings on a high resolution magnetic resonance imaging (MRI) scan.     

Quantification of aortic stenosis in mechanically ventilated patients using multiplane transesophageal Doppler echocardiography

OBJECTIVE: The development of sudden postoperative hearing loss as a complication of microvascular decompression (MVD) operations in the cerebellopontine angle has already been reported. A sudden hearing loss of vascular origin may also occur hours or days after such operations, but even in such cases an improvement of hearing over the following weeks is possible. Here we report on a gradual deterioration of hearing over a period of two weeks after MVD which has not been described in the literature up to now. CLINICAL PRESENTATION: A MVD operation was performed twice on a 36 year old patient with trigeminal neuralgia. After the second operation the patient developed a slight hearing impairment 3 days postoperatively which increased over a period of two weeks and ended up with total deafness. The course of intra-operative brainstem auditory evoked potentials and postoperative audiograms is documented. CONCLUSION: Because of gradual development of the delayed hearing loss, we conclude that postoperative tissue scarring may be the underlying pathology.     

Lateral femoral cutaneous neuropathy: paresthetic meralgia. Neurophysiological diagnosis

INTRODUCTION: The neurophysiological approach to meralgia paresthetica (MP) deals with the possible abnormalities demonstrated in the peripheral nerve conduction and/or somatosensory evoked potentials (SEP) of the lateral femoral cutaneous nerve (LFCN). MATERIAL AND METHODS: To ascertain the diagnostic value of these methods, a group of 23 patients with unilateral MP symptoms has been studied; SEP of LFCN was also evaluated in a series of normal people. RESULTS: LFCN conduction was abnormal on the symptomatic side in 47.6% of the cases and nerve potential was absent on both sides in all the rest. SEPLFCN showed some impairment in 91% of the cases on the symptomatic side and responses were obtained on the asymptomatic side in every case; the most common abnormality was the delay of the response followed by its followed by its absence. In the normal group, the amplitude of potentials registered on the contralateral scalp to the stimulated side was usually higher than that registered on the median line, where they eventually lacked. Methodologically, this fact supports the need of a multiple recording of the SEPLFCN on the scalp. CONCLUSIONS: The SEPLFCN should be considered as the main technique for the objective diagnosis of MP and although LFCN conduction can supply useful information in individual cases, its exclusive use may lead to rather many positive false results.     

Glutathione reductase, selenium-dependent glutathione peroxidase, glutathione levels, and lipid peroxidation in freshwater bivalves, Unio tumidus, as biomarkers of aquatic contamination in field studies

Somatosensory evoked potential (SEP) recordings in patients suffering from cortical myoclonus (CM) are characterised by evidence of abnormally enhanced scalp components. Our aim was to verify whether enhanced activity in giant SEPs arises from the same generators as in healthy subjects. We used the brain electrical source analysis (BESA) to compare scalp SEP generators of healthy subjects to those calculated in 3 patients with CM of varying causes. Firstly, we built a 4-dipole model explaining scalp distribution of early SEPs in normal subjects and then applied it to traces recorded from CM patients. Our model, issued from the right median nerve grand average and applied also to recordings from single individuals, included a dipole at the base of the skull and three other perirolandic dipoles. The first of the latter dipoles was tangentially oriented and was active at the same latencies as the N20/P20 potentials and, with opposite polarity, the P24/ N24 responses; the second dipole explained the central P22 distribution and the third had a peak of activity corresponding to the N30 component. When we applied our 4-dipole model to CM recordings, the first perirolandic dipole had a third peak of activity in all patients at the same latency as a parietal negativity and a frontal positivity, both following giant P24/N24 components; on the other hand, in one patient the second perirolandic dipole showed a later activation corresponding to a high central negativity, following a giant P22 response. We suggest that only the initial giant SEPs correspond to physiological potentials evoked in healthy subjects. The occurrence of late giant SEPs could be explained by hyperpolarization, following the postsynaptic excitatory potentials responsible for the early giant components.     

Microvascular decompression in glossopharyngeal neuralgia

Glossopharyngeal neuralgia is a rare and often controversial cause for odynophagia and otalgia. The otolaryngologist, head and neck surgeon may be the primary physician called upon to diagnose and treat this entity. In this study, vascular decompression, or more specifically, elimination of contact between the ninth cranial nerve and the posterior inferior cerebellar artery, was employed as treatment in three patients. All achieved relief of their symptoms with this intervention. A review of the neurosurgical literature and the experience with vascular decompression in trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia is presented. The authors conclude that vascular decompression is effective in carefully selected patients, and the role of the skull base surgeon in managing this problem is expanding.     

Hemifacial spasm: clinical findings and treatment

Hemifacial spasm (HFS) is a peripherally induced movement disorder characterized by involuntary, unilateral, intermittent, irregular, tonic or clonic contractions of muscles innervated by the ipsilateral facial nerve. We reviewed the clinical features and response to different treatments in 158 patients (61% women) with HFS evaluated at our Movement Disorders Clinic. The mean age at onset was 48.5+/-14.1 years (range: 15-87) and the mean duration of symptoms was 11.4+/-8.5 (range: 0.5-53) years. The left side was affected in 56% instances; 5 patients had bilateral HFS. The lower lid was the most common site of the initial involvement followed by cheek and perioral region. Involuntary eye closure which interfered with vision and social embarrassment were the most common complaints. HFS was associated with trigeminal neuralgia in 5.1% of the cases and 5.7% had prior history of Bell's palsy. Although vascular abnormalities, facial nerve injury, and intracranial tumor were responsible for symptoms in some patients, most patients had no apparent etiology. Botulinum toxin type A (BTX-A) injections, used in 110 patients, provided marked to moderate improvement in 95% of patients. Seven of the 25 (28%) patients who had microvascular decompression reported permanent complications and the HFS recurred in 5 (20%). Although occasionally troublesome, HFS is generally a benign disorder that can be treated effectively with either BTX-A or microvascular decompression.     

Clinical application for gene therapy in prostate cancer

We report a patient with peripheral neuropathy caused by cisplatin for the treatment of testicular tumor. Routine studies of nerve conduction and somatosensory evoked potentials demonstrated large myelinated fiber neuropathy suggesting ganglioneuronopathy. We also performed a CO2 laser evoked potential study, and found that small myelinated fibers, which are related to pain sensation, were well preserved in this patient.     

Mucin-producing tumor of the pancreas: diagnostic value of diffusion-weighted echo-planar MR imaging

It is generally accepted that hemifacial spasm (HFS) and trigeminal neuralgia are caused by compression of the facial nerve (seventh cranial nerve) or the trigeminal nerve (fifth cranial nerve) at the nerve's root exit (or entry) zone (REZ); thus, neurosurgeons generally perform neurovascular decompression at the REZ. Neurosurgeons tend to ignore vascular compression at distal portions of the seventh cranial nerve, even when found incidentally while performing neurovascular decompression at the REZ of that nerve, because compression of distal portions of the seventh cranial nerve has not been regarded as a cause of HFS. Recently the authors treated seven cases of HFS in which compression of the distal portion of the seventh cranial nerve produced symptoms. The anterior inferior cerebellar artery (AICA) was the offending vessel in five of these cases. Great care must be taken not to stretch the internal auditory arteries during manipulation of the AICA because these small arteries are quite vulnerable to surgical manipulation and the patient may experience hearing loss postoperatively. It must be kept in mind that compression of distal portions of the seventh cranial nerve may be responsible for HFS in cases in which neurovascular compression at the REZ is not confirmed intraoperatively and in cases in which neurovascular decompression at the nerve's REZ does not cure HFS. Surgical procedures for decompression of the distal portion of the seventh cranial nerve as well as decompression at the REZ should be performed when a deep vascular groove is noticed at the distal site of compression of the nerve.     

Intraoperative electroneurodiagnostics (transcranial electrical motor evoked potentials) to evaluate the functional status of anterior spinal roots and spinal nerves during brachial plexus surgery

Intradural spinal root lesions cannot be recognized by dissecting the brachial plexus and lead to ineffective surgery if they remain undetected. Therefore, patients need to undergo a diagnostic procedure to assess the intradural status of the spinal roots. Although motor recovery is the main goal of brachial plexus surgery, the techniques currently applied do not permit adequate evaluation of the anterior root. In search of an alternative, we performed intraoperative motor evoked potentials. Ninety spinal nerves in 19 patients suffering from brachial plexus lesions were dissected. Twenty-seven spinal nerves were avulsed; 8 nerves were disrupted and 17 were completely scarred, resulting in 25 stumps. Thirty-eight nerves appeared to be undamaged. On central stimulation, nerve compound action potentials were recorded from the exposed spinal nerves. Nerve compound action potentials could only be recorded from 21 stumps and from 32 apparently undamaged nerves. No recordings were obtained from 4 stumps and 7 spinal nerves in continuity. According to these findings, it is highly probable that surgery would have been insufficient in 10 spinal nerves if intraoperative motor evoked potentials had not been performed. We conclude that (1) intraoperative motor evoked potentials are an effective means for investigating the functional status of anterior motor roots and motor fibers in exposed spinal nerves, and (2) the use of motor evoked potentials should be considered during brachial plexus surgery to improve interventions.     

Abnormal sensory nerve conduction in multifocal demyelinating neuropathy with persistent conduction block

Two patients exhibited chronic, slightly asymmetric weakness and wasting with fasciculations of the upper limb and hand muscles. Motor nerve conduction studies showed features of multifocal conduction block in nerve segments other than those usually involved in entrapment syndromes. The F wave was markedly delayed in the median and ulnar nerves. Transcranial cortical and cervical root magnetic stimulation showed bilaterally delayed thenar responses with normal central conduction time. Needle electromyography demonstrated a chronic denervation pattern with large polyphasic motor units in several muscles of the upper limbs. Sensory symptoms were mild and limited to paresthesias in the fingertips. Sensory nerve conduction velocity and sensory nerve action potential amplitudes were normal in elbow-to-wrist and wrist-to-finger segments of the median and ulnar nerves, but there was a delayed cortical response and unrecognizable Erb's point and cervical responses in the somatosensory evoked potentials to median nerve electrical stimulation. Electrophysiologic examination was normal in most nerves of the lower limbs. These two patients, meeting clinical and electrophysiologic criteria of multifocal neuropathy with conduction block, demonstrate that sensory fibers may also be involved in this syndrome.     

AAEM minimonograph 32: the electrodiagnostic examination in patients with radiculopathies. American Association of Electrodiagnostic Medicine

The anatomy and pathophysiology of radiculopathies are reviewed, and the electrodiagnostic approaches used in evaluating patients with suspected root lesions are discussed. Such electrophysiologic procedures include motor and sensory nerve conduction studies, late-response studies, somatosensory and motor evoked potentials, nerve root stimulation, and needle electromyography. The value and limitations of these different procedures are considered. At the present time, needle electromyography is the single most useful approach. The findings in patients with radiculopathies at different levels are summarized.     

Differentiating attention-deficit/hyperactivity disorder from pervasive developmental disorder not otherwise specified

To discriminate between the various compressing vessels of the facial nerves in patients with hemifacial spasm, pre-operative oblique sagittal gradient-echo MR imaging was performed. Forty-two patients underwent pre-operative MR imaging and microvascular decompression. The MR images were divided according to findings into three groups as follows: Group A, a thick and/or long high-intensity line along the root exit zone (REZ) of the facial nerve; Group B, a thin and/or short high-intensity line along the REZ; and Group C, an unreliable image around the REZ. Fifteen images were classified as Group A, 19 as Group B, and 8 as Group C. In Group A, vertebral artery (VA) compression was confirmed intra-operatively in 12 cases and posterior inferior cerebellar artery (PICA) or anterior inferior cerebellar artery (AICA) compression in 3. In Group B, PICA or AICA compression was confirmed intra-operatively in all cases. In Group C, PICA or AICA compression was confirmed intra-operatively in 7 cases and no compression in one. In all cases of VA compression of the facial nerve, the oblique sagittal gradient-echo images demonstrated a thick and/or long high intensity line along the REZ. Oblique sagittal gradient-echo MR imaging is a useful preoperative planning aid, which can predict the possibility of VA compression prior to microvascular decompression for hemifacial spasm.     

The place of ganglion or root alcohol injection in trigeminal neuralgia

Of 157 patients with trigeminal neuralgia, referred for neurosurgery, 81 underwent 85 ganglion or root injections. The results, which are analysed with regard to pain relief and sensory loss, compare favourably with results from the literature of other forms of surgery, particularly open temporal root section.     

Trigeminal neuralgia: retrolabyrinthine selective posterior root section

Experience gained from the treatment of 41 patients with 42 operations for the relief of Vth nerve pain over the past 5 years is reported. For the selective section of the posterior root of the trigeminal nerve 28 retrolabyrinthine procedures were performed for typical tic douloureux with complete lasting relief in 25; 1 was relieved with the addition of aspirin; and 2 were relieved by Tegratol even though it was ineffective before surgery. There were no deaths and no serious complications. None had facial paralysis or anesthesia dolorosa. The retrolabyrinthine approach to the posterior root of the trigeminal nerve is ideally suited for those patients with refractory tic douloureux or patients with facial pain secondary to other causes such as tumor. Because of its effectiveness and low morbidity, this procedure offers advantages over other surgical techniques.