Location of motoneurons supplying individual muscles in normal and grafted supernumerary limbs of Xenopus laevis.

The purpose of this study was to investigate innervation of transplanted supernumerary hindlimbs in the frog (Xenopus laevis). Motoneurons innervating identified muscles in normal and supernumerary limbs were located by the method of retrograde transport of HRP after intramuscular injection. In the lumbar spinal cord of normal Xenopus, motoneurons supplying medial hindlimb muscles, which are derived from the ventral muscle mass during development, are located at the medial end of the motor column; those innervating lateral, dorsally-derived muscles, lie at the lateral end of the motor column. In animals with supernumerary limbs, motoneurons supplying the transplant usually occupied the same mediolateral position as those supplying the same muscle in the normal limb. However, the rostrocaudal location of these motor pools exhibited greater flexibility. When the transplant was innervated by a rostral nerve of the lumbar plexus, motoneurons supplying gastrocnemius could be located in a region of the spinal cord whose motoneurons do not normally innervate this muscle. There is thus no rigid requirement that gastrocnemius motoneurons be located at specific segmental levels. Motoneurons supplying gastrocnemius in the normal limb on the experimental side showed normal rostrocaudal distributions, indicating little rearrangement of these motor pools. Dorsal root ganglion cells labeled after HRP injection could be concentrated in a ganglion which normally supplies little or no innervation to the injected muscle. The location of these cells confirmed the segmental source of sensory innervation of the extra limb; i.e., there was no stray innervation. Animals with supernumerary limbs exhibited little or no increase in the number of motoneurons on the extra limb side. In contrast, dorsal root ganglion cell populations exhibited a large increase on the experimental side.

Facial trigeminal synkinesis associated with a trigeminal schwannoma.

The authors describe the clinical and electrophysiologic findings in a patient with synkinesis between muscles innervated by the facial and trigeminal nerves after resection of a trigeminal schwannoma. Conventional facial nerve conduction and blink reflex studies were normal. Stimulation of the supraorbital and facial nerves elicited reproducible responses in the masseter and pterygoid muscles, confirming a peripheral site of aberrant regeneration of the facial and trigeminal nerves.

Arteritis and brachial plexus neuropathy as delayed complications of radiation therapy.

Radiation-induced arteritis of large vessels and brachial plexus neuropathy are uncommon delayed complications of local radiation therapy. We describe a 66-year-old woman with right arm discomfort, weakness, and acrocyanosis that developed 21 years after local radiation for breast adenocarcinoma. Arteriography revealed arteritis, with ulcerated plaque formation at the subclavian-axillary artery junction, consistent with radiation-induced disease, and diffuse irregularity of the axillary artery. Electromyography showed a chronic brachial plexopathy. The patient's acrocyanosis, thought to be due to digital embolization from her vascular disease, improved with antiplatelet therapy. The concurrent combination of radiation-induced arteritis and brachial plexopathy is uncommon but should be considered in patients presenting with upper extremity pain or weakness after radiation therapy.

Effect of multiple intravenous injections of diatrizoate on iodine concentrations and osmolality. An experimental study in rabbits.

Multiple intravenous injections of contrast media are used in radiology, but information regarding corresponding changes in the serum iodine concentrations and osmolality is lacking. We measured the changes in serum iodine concentration and serum osmolality in rabbits after a series of intravenous injections of contrast media. Hypaque-76 (1 cc/kg) was injected intravenously in awake rabbits at 10-minute intervals for 1 hour and arterial blood sampled at midpoint times between injections. During the 1-hour period of seven serial injections, mean serum iodine concentration at 5 minutes was 2.3 mg I/cc (+/- 0.1 SEM, n = 14); at 35 minutes, 5.1 mg I/cc (+/- 0.2); and at 65 minutes, 6.7 mg I/cc (+/- 0.4). The mean peak concentration was 6.8 mg I/cc (+/- 0.4). Serum osmolality underwent a mean increase of 16 mosm/kg during the injection period. Hypertonic mannitol injections produced a smaller increase in osmolality (10 mosm/kg). Isotonic saline injections in control animals produced no change in osmolality.

Reversible akinetic mutism possibly induced by baclofen.

A 76-year-old man developed akinetic mutism after 3 days of receiving low-dosage baclofen. Electroencephalography showed a diffusely slow background with intermittent generalized sharp wave discharges. The condition resolved after discontinuing baclofen. To our knowledge, this is the first reported case of baclofen-induced akinetic mutism in a patient with normal renal function. The pathophysiology of this condition is unknown, but it may result from selective binding of the drug to the gamma-aminobutyric acid-B receptors located in the frontal lobes or thalamic nuclei, interrupting the thalamocortical limbic pathways.

Neuralgic amyotrophy: clinical features and diagnostic evaluation.

BACKGROUND: Neuralgic amyotrophy is an uncommon neurologic syndrome of unknown etiology involving the brachial plexus, which is manifest by shoulder and arm pain, weakness, and sensory loss. Because of the diversity and variability of the initial features and similarity to other neurologic and non-neurologic disorders, patients may initially present to internists, orthopedic surgeons, or pulmonologists, and may be initially diagnosed with an alternative disorder. REVIEW SUMMARY: Neuralgic amyotrophy occurs at an annual incidence rate of 1 to 2 cases per 100,000 population. The disorder is most common in adulthood, but patients of any age may be affected. Pain is the most common initial symptom and is followed by weakness and sensory loss in the distribution of a single nerve or diffuse regions of the brachial plexus. Although the exact etiology is unknown, many associated factors, such as immunizations, minor trauma, infectious diseases, pregnancy, and surgical procedures have been associated with the development of the disorder. Evaluation with electrodiagnostic and radiographic studies is useful in confirming the diagnosis and excluding alternative disorders. No treatment has been definitively proven to improve the course of the disorder; however, the overall prognosis is good, with approximately 90% of patients demonstrating significant improvement. CONCLUSIONS: Neuralgic amyotrophy is an important, potentially debilitating disorder, which may present to physicians in multiple specialties. Awareness of this disorder may preclude unnecessary testing or surgical procedures and can guide toward appropriate treatment with physical therapy. Counseling patients about the overall good prognosis can help appease patients' anxiety about a more sinister diagnosis or course.

Subacute sensory neuropathy associated with Epstein-Barr virus.

A 35-year-old man experienced severe sensory loss, pseudoathetosis, and areflexia during recovery from a severe viral illness. Sensory nerve action potentials were absent, motor conduction velocities were mildly slowed, and blink reflexes were normal. Magnetic resonance imaging (MRI) revealed abnormal signal within the central and dorsal aspects of the thoracic cord. Acute and convalescent Epstein-Barr virus (EBV) titers suggested EBV as the etiology. Subacute sensory neuropathy, with peripheral and central nervous system involvement, is a rare complication of EBV infection.

Electrophysiologic findings in amyloid myopathy.

Myopathy is an uncommon manifestation of systemic amyloidosis. A retrospective chart review of 17 patients seen between 1975 and 1997 with biopsy-proven amyloid myopathy was performed to characterize the electrophysiologic features. Nerve conduction study abnormalities occurred in 14 of 17 patients (82%). The most common abnormality was a low peroneal and/or tibial compound muscle action potential amplitude (n = 9). Mild abnormalities also occurred in seven other nerves. Repetitive stimulation at 2 Hz in 10 nerves was normal. Electromyography demonstrated fibrillation potentials in 69% of muscles, most frequently in the gluteus medius (90%) and paraspinals (87%). The fibrillation potentials were sparse in 60%. Short-duration, low-amplitude motor unit potentials (MUPs) were found in 72% of the muscles examined, were mild in 81%, and were more common in proximal muscles. Long-duration MUPs were found in 19% of muscles and a mixed population of MUPs in 4%. These findings are similar to those of common chronic, inflammatory myopathies.

Outcome of peroneal neuropathies in patients with systemic malignant disease.

BACKGROUND: Peroneal neuropathies in patients with systemic cancer previously have been attributed to weight loss, but to the authors' knowledge other associated conditions have not been assessed, and the outcome of peroneal neuropathies in cancer patients has not been studied. METHODS: A retrospective chart review of patients evaluated at the Mayo Clinic between 1984 and 1993 with systemic malignant disease and a clinical diagnosis of peroneal neuropathy was performed to define factors associated with peroneal neuropathies and to assess outcome. All patients underwent neurologic examination and electromyography. RESULTS: Fifty-eight patients with systemic malignant disease were found to have a peroneal neuropathy. Peroneal neuropathies occurred more often in men (45 patients) than in women (13 patients). The median age of the patients was 70 years. The most common cancers were hematologic (12 patients) and pulmonary (11 patients), followed by tumors of the prostate (8 patients), gastrointestinal tract (7 patients), transitional cell (5 patients), breast (5 patients), and colon (5 patients), as well as sarcomas and melanoma (5 patients). The median time to the diagnosis of peroneal neuropathy after the diagnosis of cancer was 5 months. At the time of diagnosis, 34 patients had severe deficits, 19 had moderate deficits, and 5 had mild deficits. Associated factors included weight loss (occurring in 60% of patients), leg crossing (35% of patients), recent chemotherapy (16% of patients), cutaneous vasculitis (5% of patients), and local metastatic lesions (3% of patients). In nearly 50% of patients, peroneal neuropathy improved (25.9%) or resolved (22.4%). In 39.7% of patients, follow-up was inadequate because death occurred soon after diagnosis. Of the patients with adequate follow-up before death, 80% had either improvement (42.9%) or resolution (37.1%). CONCLUSIONS: For those patients with systemic malignant disease in whom peroneal neuropathy develops, the outcome of the neuropathy is good, with the majority of patients achieving partial or complete resolution.