Serial evoked potential studies and MRI imaging in chronic progressive multiple sclerosis

Measurements of serial evoked potential latencies and plaque burden on MRI scans are often obtained during clinical studies of multiple sclerosis patients to provide additional information to the disability-based primary endpoints. The ideal laboratory-based marker of progression would be expected to significantly change over the time period of study. Serial visual (VEP) and brainstem auditory evoked potentials (BAEP) and MRI scans of 11 chronic progressive MS patients were obtained over a 1.5 year period in a clinical study. Over this period, there was no significant change in disability as measured by the Kurtzke EDSS, Ambulation Index or Neurological Rating Score. The VEP P100 significantly progressed over the period of study. However, the MRI T(2) plaque burden and BAEP I-V intrapeak latency did not significantly progress over the 1.5 years. We conclude that, in chronic progressive MS, serial visual evoked potential tests may complement standard disability-based endpoints to assess disease progression.

A double-blind, placebo-controlled trial of extracorporeal photopheresis in chronic progressive multiple sclerosis

Extracorporeal photopheresis is a safe therapy for cutaneous T-cell lymphoma and may have efficacy in certain autoimmune disorders. We performed a randomized, double-blinded, placebo-controlled trial of monthly photopheresis therapy in 16 patients with clinically definite multiple sclerosis (MS). All patients had progressed during the preceding year with entry Expanded Disability Status Scale (EDSS) scores between 3.0 and 7.0. Patients received photopheresis or sham therapy for 1 year and were followed for an additional 6 to 12 months. Patients were clinically evaluated by three disability scales: (1) EDSS; (2) Ambulation index and (3) Scripp's quantitative neurologic assessment. No serious side effects occurred in either group. There were no differences between the photopheresis and sham therapy groups by the disability measures. Additionally, there were no differences in progression of MRI plaque burden or evoked potential latencies. In this limited study, photopheresis was found to be safe but did not significantly alter the course of chronic progressive MS.

Iatrogenic superior gluteal mononeuropathy

Injuries to the superior gluteal nerve (SGN) have been reported as a result of trauma, pyriformis muscle entrapment, injections, and lumbar lordosis and inadequate back stabilization. We report 3 patients who developed isolated SGN injuries, 1 after a partial nephrectomy and 2 following revision of a total hip arthroplasty. SGN should be suspected in anyone developing an abnormal gait after hip or pelvic surgery or after prolonged lateral decubitus positioning.

Bulbocavernosus reflex studies and autonomic testing in the diagnosis of erectile dysfunction

The electrophysiologic evaluation of patients with erectile dysfunction presents an important diagnostic challenge. The bulbocavernosus reflex (BCR) latency has been commonly used to evaluate these disorders. However, it is a measure of somatic penile innervation, whereas erection is primarily dependent on autonomic function. We evaluated 195 men with erectile dysfunction over a 3 year period. Each had electrophysiologic studies, nerve conduction studies and a BCR. BCR studies were abnormal in only 7%, of which most had diabetes or pelvic trauma. The BCR was the sole electrophysiologic abnormality in only 2%. Autonomic testing (AT) was additionally performed in 19 diabetic and 23 non-diabetic patients. This included sympathetic skin responses and measurement of the Valsalva ratio and heart rate variability with 6/min breathing. In the diabetic group, AT was positive in 63%, and most often was the sole abnormality. The bulbocavernosus reflex is relatively insensitive in the diagnosis of erectile dysfunction. Brief autonomic testing may provide valuable additional data, particularly in diabetics.

Autosomal dominant transmission of Dejerine-Sottas disease (HMSN III)

Hereditary motor-sensory neuropathy type III (HMSN III) (Dejerine-Sottas disease) is a severe demyelinating neuropathy that is traditionally considered autosomal recessive. We report a father and daughter diagnosed with HMSN III by clinical, electrophysiologic, and pathologic criteria, thus showing that it may be transmitted in an autosomal dominant fashion in selected families.

Direct muscle stimulation in acute quadriplegic myopathy

We have previously found that muscle is electrically inexcitable in severe acute quadriplegic myopathy (AQM). In contrast, muscle retains normal electrical excitability in peripheral neuropathy. To study the relationship between muscle electrical excitability and all types of flaccid weakness occurring in the intensive care unit, we identified 14 critically ill, weak patients and measured the amplitude of compound muscle action potentials (CMAPs) obtained with direct muscle stimulation (dmCMAP) and with nerve stimulation (neCMAP). In 11 of 14 patients dmCMAP amplitudes were reduced and the ratio of the neCMAP amplitude to the dmCMAP amplitude (nerve/muscle ratio) was indicative of loss of muscle electrical excitability. In 2 other patients, the nerve/muscle ratio indicated neuropathy. Direct muscle stimulation may allow differentiation of AQM from neuropathy even in comatose or encephalopathic critically ill patients. AQM may be more common than has previously been appreciated.

Posterior cervical spinal cord infarction following vertebral artery dissection

There are only two reported cases of unilateral posterior cervical spinal cord infarction as a result of vertebral artery dissection. We describe the first reported case of bilateral posterior spinal cord infarction caused by vertebral artery dissection.

Chronic inflammatory demyelinating polyneuropathy associated with malignant melanoma

We report three patients who developed chronic inflammatory demyelinating polyneuropathy (CIDP) in association with malignant melanoma. In two cases, melanoma was discovered during the initial evaluation for neuropathy. Two patients also had vitiligo, an antibody-mediated disorder that may complicate melanoma. Melanoma cells and Schwann cells are both of neuroectodermal cell origin, with shared surface antigens. Shared immunoreactivity may account for the association between melanoma and CIDP, as with vitiligo.

Muscle is electrically inexcitable in acute quadriplegic myopathy

We directly stimulated muscle in three patients with acute quadriplegic myopathy to determine whether paralyzed muscle in this syndrome is electrically excitable. Two of the patients had been treated with neuromuscular blocking agents and corticosteroids, and one patient had been treated with corticosteroids alone. We found that paralyzed muscle is electrically inexcitable in affected patients. Muscle regained electrical excitability over weeks to months. The recovery of muscle excitability paralleled the clinical recovery of patients, suggesting that paralysis in this syndrome is secondary to electrical inexcitability of muscle membrane.

Site of autonomic dysfunction in a patient with Ross' syndrome and postganglionic Horner's syndrome

Ross' syndrome is a rare peripheral nervous system disorder defined by Adie's tonic pupil, hyporeflexia, and segmental anhidrosis. Injury to postganglionic cholinergic fibers is believed to account for the tonic pupil and sweating disturbance. We report a 47-year-old man found to have Ross' syndrome in combination with a complete postganglionic Horner's syndrome. Pharmacologic and sudomotor tests in this unique patient provide further evidence that Ross' syndrome results from injury to sympathetic and parasympathetic ganglion cells or to their postganglionic projections.

Mechanism of lysosome rupture by dipeptides

Low concentrations of some neutral dipeptides, such as L-Ala-L-Ala, rapidly disrupt rat liver lysosomes. The phenomenon has been attributed to an osmotic imbalance generated by the production of amino acids in the lysosome by lysosomal dipeptidase activity. This hypothesis is challenged by testing several pairs of dipeptides available in both D- and L-forms and a range of dipeptides whose susceptibility to lysosomal dipeptidase activity is known. A good correlation was found between the lytic ability of dipeptides and their capacity to cross the lysosome membrane and be hydrolysed by lysosomal dipeptidase. The osmotic-imbalance hypothesis is critically evaluated in the light of the results and of recent information concerning the carrier-mediated transport of amino acids and dipeptides across the lysosome membrane. It is concluded that intralysosomal generation of amino acids remains the most plausible explanation of the lytic activity of dipeptides, and that the dipeptide porter(s) in the lysosome membrane must have higher Km than the amino acid porters.

Prolonged muscle weakness after neuromuscular blockade in the intensive care unit

As noted, quadriparesis with reduced reflexes and difficulty with ventilator weaning may be seen as a result of a number of neuromuscular disorders. The clinical approach relies on exclusion of a central cause first, followed by careful examination of peripheral nerve and muscle function. Persistent neuromuscular blockade should be excluded initially because it is a readily reversible condition. Use of a train of four stimulation with a peripheral twitch monitor can quickly establish integrity of conduction across the neuromuscular junction. If necessary, further electrophysiologic studies allow differentiation among the relevant diagnostic possibilities. CIP is characterized by nerve conduction and EMG findings consistent with axonal degeneration of sensory and motor fibers. GBS is distinguished by evidence of demyelination on nerve conduction studies, in addition to elevated spinal fluid protein. Persistent neuromuscular blockade is identified by a decremental response on repetitive stimulation studies of neuromuscular transmission. The acute myopathy following neuromuscular blockage does not involve sensory responses. Needle EMG examination reflects a myopathic pattern, rather than a neurogenic one as seen in CIP or GBS. In myopathic patients who are unable to move their limbs at all (precluding a full EMG examination), a muscle biopsy identifies muscle as the site of involvement.

Spontaneous remission of a third-nerve palsy in meningeal lymphoma

We report on a patient with spontaneous remission of a third-nerve palsy who was subsequently found to have meningeal lymphoma. Initial magnetic resonance images (MRI) showed bilateral enhancement of the third nerves. Follow-up MRI 7 months later, without treatment, showed complete resolution. One year after initial presentation, the patient developed multiple lumbosacral radiculopathies and examination of a nerve root biopsy specimen disclosed a B-cell lymphoma. Serial cerebrospinal fluid analyses over the previous year showed occasional atypical cells, later found to resemble closely the biopsy cell type. We conclude that meningeal lymphoma may have a protracted course, with spontaneous remission of both clinical and neuroimaging findings.

Stimulated single-fiber electromyography in Lambert-Eaton myasthenic syndrome

The Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder of neuromuscular transmission. Electrodiagnosis is confirmed by an increase in compound muscle action potential amplitude during high-frequency repetitive nerve stimulation or following brief exercise. We describe the results of stimulated single-fiber electromyography in 4 patients with disorders of neuromuscular transmission: LEMS (2), LEMS/myasthenia gravis (MG) overlap (1), and MG (1). Stimulated SFEMG was performed in the extensor digitorum communis muscle with axonal intramuscular suprathreshold stimulation at low and high rates. In all 4 patients, a rate dependence of jitter was found. In LEMS and LEMS/MG, jitter and blocking improved with high stimulation rates, as compared with the opposite effect in MG. We conclude that stimulated SFEMG is a valuable technique in the diagnosis of LEMS.