F wave parameters and F tacheodispersion in mild diabetic neuropathy.

F tacheodispersion and some F wave parameters have previously been suggested to be useful in the detection of peripheral nerve involvement in diabetic patients with normal nerve conduction studies. In this study, ulnar and tibial F wave parameters of diabetic cases with normal motor and sensory nerve conduction studies (Group 1) were calculated, F tacheodispersion histograms were constructed and compared with the same parameters obtained from the normal controls (Control group) and diabetic cases with abnormal motor and sensory nerve conduction examinations (Group 2). There was a tendency towards lower conduction velocities in ulnar and tibial tacheodispersion histograms of Group 1 and Group 2, as compared to Control group. Most of the F wave values were significantly abnormal in Group 2 in comparison to other two groups, whereas statistically significant differences between Group 1 cases and Control group were found in minimum ulnar F wave conduction velocity (FCVmin), mean ulnar FCV (FCVmean), tibial FCVmin and tibial FCVmean values. Unlike other methods, F waves give information about the entire length of the motor nerve fiber. In mild neuropathies, in which nerve fibers are damaged uniformly, testing the whole length of a nerve with this method may be beneficial in detection of a mild conduction abnormality.

Neuromuscular consequences of prolonged hunger strike: an electrophysiological study.

OBJECTIVES: The purpose of this study was to determine the electrophysiological consequences of neuromuscular and central nervous system involvement in a group of patients presented with the neurological complications of a long-term hunger strike (HS). METHODS: Motor and sensory nerve conduction (NCV), F wave, somatosensory evoked potential (SEP) and motor evoked potential (MEP) studies were performed in 12 male and 3 female patients (mean age: 29.4) following HS. RESULTS: All patients whose weight loss was 11-31 (mean: 22.8) kg after 69-day HS, had neurological findings consistent with Wernicke's encephalopathy or Wernicke-Korsakoff syndrome. Abnormally prolonged latency and/or low amplitude sensory nerve action potentials were found in 7 patients. The amplitudes of compound muscle action potentials were significantly reduced in ulnar, median and tibial motor NCV studies as compared to the controls. F waves elicited by median nerve stimulation at wrist and muscle responses evoked by cervical and lumbar magnetic stimulation had significantly prolonged latencies. MEPs recorded from the lower extremities showed a slight prolongation in central conduction times. The cortical response latencies were prolonged in tibial SEPs. CONCLUSIONS: The most prominent finding in this patient group was the low amplitude of CMAPs elicited in motor NCV studies which was concluded to be resulted from the reversible muscular changes. The other electrophysiological findings suggested that peripheral nerves and long central nervous system pathways were also mildly involved.

Magnetic nerve root stimulation in two types of brachial plexus injury: segmental demyelination and axonal degeneration.

Magnetic cervical nerve root stimulation was performed in 9 patients with plexopathies secondary to suspension (SP) and in 12 cases with neurogenic thoracic outlet syndrome (NTOS). The findings were compared with those of the previously reported case groups: n-hexane polyneuropathy (HPNP), inflammatory demyelinating polyneuropathy (IDP), and motor neuron disease (MND). Muscle responses elicited by magnetic stimulation had very high rates of amplitude and area loss in the neck-axilla segments of the 6 SP patients. This, along with the other electrophysiological findings, suggested the presence of segmentally demyelinating plexus lesions. In NTOS patients, magnetic stimulation findings were not significantly different from those of the controls. Neck-axilla segment amplitude and are reduction rates in SP and IDP patients were significantly higher than those found in NTOS, HPNP, and MND groups, implying that magnetic nerve root stimulation may have a role in the demonstration of segmentally demyelinating lesions involving proximal nerve segments.

Electrophysiological findings in patients who received radiation therapy over the brachial plexus: a magnetic stimulation study.

Clinical and electrophysiological findings of 47 asymptomatic females who received radiation therapy (RT) over their brachial plexus region are presented and compared with 8 radiation-induced brachial plexopathy (RBP) and 4 neoplastic brachial plexopathy (NBP) patients. In the asymptomatic group, abnormal findings were more frequent in patients whose post-RT period was longer than 1 year. Flexor carpi radialis H reflex was delayed or absent in 19 patients (52%) in this subgroup of asymptomatic cases, as compared to only 2 (18%) of the patients with post-RT periods of less than 1 year. Magnetic cervical nerve root stimulation was performed in 16 asymptomatic cases, with the conclusion that there was no significant difference between the irradiated and non-irradiated sides with regard to latencies, amplitudes and areas of the muscle responses. In spite of this, muscle response amplitudes and areas on both sides were significantly lower than those obtained from healthy controls. It was postulated that this finding resulted from hypoexcitability to magnetic stimulation produced by slight nerve root damage. Any part of the brachial plexus could be affected in RBP and NBP patients. Myokymic discharges were found at a high rate (87.5%) in RBP group. Cervical magnetic nerve root stimulation may have a diagnostic value in these patients in localizing the nerve lesion over the brachial plexus.

Peripheral and central conduction in n-hexane polyneuropathy.

Electrophysiological findings of 27 males with industrial n-hexane polyneuropathy (HPNP) are presented. The results of needle electromyography and nerve conduction studies were compatible with primarily axonal polyneuropathy with secondary segmental demyelination. Motor conduction velocities were the slowest in distal regions of the nerves. In the proximal nerve segments, which were partly tested by magnetic stimulation of the nerve roots, this slowing was much less pronounced. The reduction in mean motor conduction velocities in the forearm segments of ulnar nerves was more than 30% in comparison to the control group means. This reduction was only 10% in the neck-axilla segments. We think that this finding is a reflection of the distal axonopathy process. Central motor conduction times calculated by transcranial magnetic stimulation and spinal nerve root stimulation were found to be prolonged in HPNP patients, indicating that descending motor pathways are affected in human HPNP.

Magnetic stimulation in hemifacial spasm and post-facial palsy synkinesis.

The facial nerve was stimulated trascranially with a magnetic stimulator in 14 normal controls, 14 hemifacial spasm patients, and 16 post-facial-palsy synkinesis patients. Magnetic stimulation in normal controls revealed muscle responses which had latencies with a mean value of 4.99 +/- 0.49 ms and amplitudes of 2.41 +/- 1.08 mV. In the same group, transosseal conduction time was calculated to be 1.20 +/- 0.13 ms. In the hemifacial spasm group, the amplitudes of the responses on the affected sides were lower as compared to the unaffected sides (mean values 1.78 vs. 2.41 mV, P = 0.01). Also, the threshold to magnetic stimulation was elevated on the affected sides. These findings are suggestive of the presence of a hypoexcitability to magnetic stimulation in the root entry zone. In the post-facial-palsy synkinesis patients, magnetic stimulation of the affected sides resulted in responses with long latencies and low amplitudes (mean latency 6.34 ms, mean amplitude 0.90 mV). In the recordings made with magnetic stimulation, the difference of the latencies between the two sides was larger as compared to those obtained by electrical stimulation. The transosseal conduction time was also remarkably prolonged on the affected side. These findings may suggest that magnetic stimulation can be an effective method of showing intracranially located lesions of the facial nerve.