Annualized incidence and spectrum of illness from an outbreak investigation of Bell's palsy.

BACKGROUND: There are limited clinical and epidemiological data on patients diagnosed with Bell's palsy. While investigating an apparent clustering of Bell's palsy, we sought to characterize the spectrum of illness in patients with this diagnosis. METHODS: A telephone survey of persons with idiopathic facial (Bell's) palsy in the Greater Toronto Area (GTA, population = 4.99 million) and Nova Scotia (population = 0.93 million) from August 1 to November 15, 1997 collected information on subject demographics, neurological symptoms, constitutional symptoms, medical investigation and management. Information regarding potential risks for exposure to infectious agents, past medical history, and family history of Bell's palsy was also collected. Subjects with other secondary causes of facial palsy were excluded. RESULTS: In the GTA and Nova Scotia, 222 and 36 patients were diagnosed with idiopathic facial (Bell's) palsy, respectively. The crude annualized incidence of Bell's palsy was 15.2 and 13.1 per 100,000 population in the GTA and Nova Scotia, respectively. There was no temporal or geographical clustering, and symptomatology did not differ significantly between the two samples. The mean age was 45 years, with 55% of subjects being female. The most common symptoms accompanying Bell's palsy were increased tearing (63%), pain in or around the ear (63%), and taste abnormalities (52%). A significant number of patients reported neurological symptoms not attributable to the facial nerve. CONCLUSION: No clustering of cases of Bell's palsy was observed to support an infectious etiology for the condition. Misdiagnosis of the etiology of facial weakness is common. Patients diagnosed with Bell's palsy have a variety of neurological symptoms, many of which cannot be attributed to a facial nerve disorder.

The spectrum of electrophysiological abnormalities in Bell's palsy.

BACKGROUND: As part of an investigation of a suspected "outbreak" of Bell's palsy in the Greater Toronto Area, a population-based sample of patients with Bell's palsy was investigated electrophysiologically to help understand the spectrum of abnormalities that can be seen in this setting. METHODS: Two hundred and twenty-four patients were surveyed, of whom 91 underwent formal neurological assessment. Of the latter, 44 were studied electrophysiologically using standard techniques. Thirty-two of the 44 patients fulfilled clinical criteria for Bell's palsy. RESULTS: A wide range of electrophysiological changes was observed. Blink responses were the most useful test showing diagnostic sensitivity of 81% and specificity of 94% compared to the contralateral control side. Needle electromyography was additionally helpful in only one patient of six with normal conduction studies. CONCLUSIONS: There is a wide spectrum of electrophysiological abnormalities in Bell's palsy. Blink reflex latencies may be under-utilized in the assessment of the facial nerve in Bell's palsy. Facial EMG is not generally useful in routine assessment.

Peripheral and autonomic nervous system involvement in chronic GM2-gangliosidosis.

GM2-gangliosidosis (McKusick 268800 and 272800) is a rare hereditary, progressive disorder of ganglioside metabolism caused by deficiency of lysosomal beta-hexosaminidase (EC 3.2.1.52) activity. It is characterized by severe central nervous system involvement. Involvement of the peripheral and autonomic nervous system has been suspected but rarely documented in published case reports in the chronic form of the disease. Four patients, aged 24-29 years, with chronic GM2-gangliosidosis were examined prospectively for evidence of peripheral and autonomic nervous system dysfunction. All had nerve conduction studies, sympathetic skin responses and cardiac monitoring during the head tilt-table test. Three patients had objective evidence of autonomic dysfunction with abnormal sympathetic nervous skin responses and axonal sensorimotor polyneuropathy. None of the patients had evidence of significant cardiovascular autonomic dysfunction on the head tilt-table test. The peripheral and autonomic nervous system may be involved in patients with chronic GM2-gangliosidosis. In some cases, this may be clinically significant. On the other hand, cardiovascular autonomic instability is apparently not a significant problem in young adult patients with the disease.

Radial entrapment neuropathy due to chronic injection-induced triceps fibrosis.

We report two patients who developed progressive, severe, painless radial neuropathies (bilateral in one, unilateral in the other) as a delayed complication of chronic intramuscular analgesic injection. In each instance, exploration of the radial nerve revealed multifocal entrapment within a densely fibrotic triceps muscle at sites between the spiral groove and distal course of the radial nerve near the elbow. Release of the nerve from constriction within the fibrotic triceps muscle produced improvement in all three affected nerves.

Endoneurial vasculitis and tubuloreticular inclusions in peripheral nerve biopsy.

We describe 3 patients in whom nerve biopsy revealed endothelial tubuloreticular inclusions in association with peripheral nerve endoneurial vasculitis. Two of the patients had systemic lupus erythematosus (SLE), while the third was HIV-positive. Review of our biopsy material featuring the much more common finding of epineurial vasculitis failed to disclose any instances in which endothelial tubuloreticular inclusions (TRIs) were present. We conclude that TRIs and endoneurial vasculitis are closely associated. Moreover, if detected on a nerve biopsy specimen, TRIs are very suggestive of SLE or HIV infection. Finally, literature evidence is cited to suggest that an "acid-labile" alpha-interferon may be pathogenically related to the vasculitic process in these patients, perhaps through a process mediated by tumor necrosis factor.

Transient absence of F-waves in acute myelopathy: a potential source of diagnostic error.

BACKGROUND: The frequent absence of F-waves in lesions of the nerve roots and proximal nerve is well known, with absence of F-waves occasionally the only electrophysiologic manifestation of early Guillain-Barré Syndrome. It is less well known that acute central nervous system lesions can cause disappearance of F-waves. CASE DESCRIPTION: A 25 year old woman presented with quadriparesis and sensory loss progressive over several days. Hyporeflexia and hypotonia were present. Imaging studies were initially negative. Electrophysiologic testing was normal apart from the diffuse absence of F-waves. This led to strong consideration of the diagnosis of Guillain-Barré Syndrome, and treatment for this diagnosis. However, imaging studies ultimately revealed the diagnosis to be transverse myelitis. F responses normalized 6 weeks after the initial study. CONCLUSIONS: F responses are significantly modulated by central nervous system factors. The relevant experimental and clinical literature is reviewed. The relevance of this to the diagnosis of Guillain-Barré Syndrome has not been previously emphasized, but our experience confirms that the absence of F-waves in a patient with acute weakness accompanied by hyporeflexia and hypotonia does not distinguish between peripheral nerve and central nervous system lesions.

MRI of the cauda equina in CIDP: clinical correlations.

Isolated reports have documented enhancement and/or enlargement of spinal nerve roots on magnetic resonance imaging (MRI) in patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). This work examines those findings in a consecutive series of 16 patients with CIDP, with blinded comparison to MRI in 13 disease controls, including five patients with Charcot-Marie-Tooth disease type 1A. MRI sequences consisted of T1 weighted sagittal and axial views, before and after administration of gadolinium. Blinded MRI interpretation was performed independently by two neuroradiologists. MRI results were correlated with data collected from chart review. Enhancement of the cauda equina was seen in 11 of 16 CIDP patients (69%), and in none of 13 control subjects. Nerve roots were enlarged, most significantly in the extraforaminal region, in three CIDP patients, and in one patient with Charcot-Marie-Tooth type 1A. MRI findings did not correlate with disease activity and severity, nor with any clinical or laboratory features in patients with CIDP.

Proximal Martin-Gruber anastomosis mimicking ulnar neuropathy at the elbow.

We present a case of Martin-Gruber anastomosis (MGA) mimicking conduction block between the above- and below-elbow sites of ulnar nerve stimulation. We review the anatomical and electrophysiological literature on this subject and discuss its clinical implications. The potential for a MGA to occur very proximally in the forearm and thus mimic ulnar neuropathy at the elbow is underrecognized. We recommend that a check for MGA be performed on all patients with an apparent conduction block at the elbow, and suggest that 3 cm distal to the medial epicondyle may be an optimal below-elbow ulnar nerve stimulation site.

IGIV in neurology--evidence and recommendations.

OBJECTIVE: To summarize the evidence for neurologic uses of immunoglobulin, intravenous (IGIV) in light of present-day clinical usage. This summary guided the development of practice recommendations for the effective and efficient use of IGIV in Neurology. METHODS: MEDLINE was searched to identify pertinent English-language review articles and original reports (n = 231) on the use of IGIV in neurology (excluding editorials, letters, and comments) published before March 1998. Evidence on alternative therapies was only included as compared to IGIV. The relevant original reports and review articles and older classic studies (n = 92) were synthesized into an information foundation. Extracted data included laboratory and clinical findings, objective measures, and clinical impressions. Clinical recommendations were based on evidence quality, graded by study design, clinical experiences of IGIV in Neurology Advisory Board members, and the conditions of IGIV use in therapy. RESULTS AND CONCLUSIONS: In neurology, many disorders are poorly understood, and the mechanisms behind beneficial regimens even less so. As a result, it is fairly common for best-practice decisions to rest on weaker evidence. The usefulness of IGIV in neurology can be described by a "combined score" based on evidence quality and strength of impact. Combined scores ranged from A+ (strongly recommended) to C (recommended as a last resort). The following clinical recommendations are made: IGIV is: strongly recommended for the treatment of Guillain-Barré syndrome (A+); favorably recommended for the treatment of chronic inflammatory demyelinating polyradiculoneuropathy, dermatomyositis, and multifocal motor neuropathy (A); recommended as a second resort for the treatment of multiple sclerosis and myasthenia gravis (B); and recommended as a last resort for the treatment of polymyositis, inclusion-body myositis, intractable epilepsies, and stiff-man syndrome (C).

Vasculitic polyradiculopathy in systemic lupus erythematosus.

A 22 year old woman with recently diagnosed systemic lupus erythematosus presented with subacute progressive areflexic paraparesis, electrophysiologically identified as a pure axonal polyradiculopathy. Sural nerve biopsy disclosed necrotising vasculitis. A striking radiological feature was marked enhancement of the cauda equina with gadolinium.

Chronic inflammatory demyelinating polyradiculoneuropathy: unusual clinical features and therapeutic responses.

We present three patients with atypical chronic inflammatory demyelinating polyradiculoneuropathy and discuss the management of patients who appear treatment resistant or present with unusual manifestations. The clinical features of the patients included massive nerve root hypertrophy causing myelopathy and movement-provoked paresthesia, pupillary dysfunction, visual loss due to increased intracranial pressure, and focal brachial plexus involvement. Each patient ultimately required prolonged courses of immune modulating therapy before benefit was attained, illustrating the importance of intensive and prolonged treatment combined with objective assessment of response to therapy.

Rapid postanoxic calcification of the basal ganglia.

A 22-year-old male diabetic on hemodialysis suffered a cerebral anoxic event. Serial CT showed the development of basal ganglia calcification over a period of no more than 17 days. It appears that the basal ganglia may develop petechial hemorrhage, necrosis, calcification, or combinations of these following an anoxic insult. The neuropathologic substrate and mechanism of rapid postanoxic calcification are unknown.

Adult peripheral neuroepithelioma in Meckel's cave.

A case of peripheral neuroepithelioma arising from the trigeminal nerve in Meckel's cave is presented. The discussion emphasizes the pathological criteria for the diagnosis of a peripheral neuroepithelioma and the current controversy about the classification of this and related tumors.

How synaptic noise may affect cross-correlations.

The relationship between a postsynaptic potential (the 'test PSP') and the profile of the cross-correlation that it produces in a repetitively discharging mammalian motoneuron, with and without synaptic noise, has been explored by computer stimulation. In a noiseless motoneuron the cross-correlation profile represents the first derivative of PSP shape except where 'shadowing' occurs (Eqn. 1a-c). When synaptic noise is present the relationship changes. When the amplitude of spike-like 'noise PSPs' occurring at regular intervals reaches a critical value (Eqn. 2), all threshold crossings involve noise PSPs. Under these circumstances termed 'just maximally effective synaptic noise', the cross-correlation represents test PSP directly (Eqn. 3a). When the interval between noise PSPs is shortened the relationship reverts to the first differential (Eqn. 4a-c). If the amplitude of the noise PSPs is less than the critical value (Eqn. 5) the cross-correlation profile is represented in a complex way by a combination of the first derivative of the upper part and the direct representation of the lower part of the test PSP. The area of the cross-correlation peak above baseline provides the most reliable estimate of EPSP amplitude in a noiseless motoneuron (Eqn. 6a). This area may fall to half for the same triangular test EPSP in the presence of just maximally effective synaptic noise (Eqn. 7a). In general, the presence of synaptic noise leads to underestimation of EPSP amplitude. These general principles remain valid for physiological noise consisting of randomly occurring EPSPs and allow certain experimental findings in cat motoneurons to be understood.

Excitability of corticospinal neurons during tonic muscle contractions in man.

A magnetic stimulus applied to the human scalp over the motor cortex causes a short latency contraction of contralateral limb muscles. This is presumed to result from the indirect excitation of corticospinal neurons with monosynaptic connections to motoneurons. The excitability of these cortical neurons can be estimated from the magnitude of the postsynaptic potentials produced in spinal motoneurons by a given magnetic stimulus. In man the characteristics of these postsynaptic potentials can be derived from changes in the firing probability of single motor units. When a subject increases the level of a sustained voluntary contraction the excitability of the corticospinal neurons estimated in this way becomes less. We conclude that the additional synaptic input to motoneurons required to maintain a stronger muscle contraction comes from fiber systems other than the population of fast corticospinal neurons activated by magnetic stimulation.