Abnormalities of proximal conduction in acute idiopathic polyneuritis: comparison of short latency evoked potentials and F-waves

Motor and sensory conduction studies, F-wave latency, and the latency of evoked potentials from the brachial plexus and cervical spine in response to median nerve stimulation were examined in 17 patients with acute idiopathic polyneuropathy. Short latency evoked potentials provided a higher yield of evidence of abnormalities of proximal conduction than did the F-wave latency. Both methods of studying conduction in the proximal segments of a peripheral nerve may be normal, however, in a small number of patients who have significant pathological lesions.

The investigation of traumatic lesions of the brachial plexus by electromyography and short latency somatosensory potentials evoked by stimulation of multiple peripheral nerves

A study of 10 patients with brachial plexus trauma was performed to determine whether the diagnostic accuracy of sensory evoked potentials (SEPs) may be improved by using stimulation of multiple peripheral nerves (median, radial, musculocutaneous and ulnar). In addition, the relative advantages of SEPs and peripheral electrophysiological studies were considered. SEP patterns following most common brachial plexus lesions were predictable. Injuries to the upper trunk affected the musculocutaneous and radial SEPs predominantly. Lower trunk or medial cord lesions primarily affected ulnar SEPs. Diffuse brachial plexus lesions affected SEPs from all stimulation sites. In the majority of cases, the necessary information was obtainable from conventional EMG: however, for lesions involving the upper segments only, SEP techniques were more useful. It is suggested that selective SEPs from appropriate peripheral nerves when interpreted in combination with conventional EMG may add useful additional information.

Visual evoked potentials in the detection of subclinical optic toxic effects secondary to ethambutol

In 14 patients with tuberculosis treated with ethambutol hydrochloride, pattern-reversal visual evoked potentials (VEPs) were recorded to monocular, whole-field stimulation before the commencement of treatment and one month and three months subsequently. In six subjects, the VEPs showed changes in the latency and amplitude of the P100 component at the one- or three-month interval. In three cases, the VEP changes reversed after cessation of treatment. In five of the six cases, changes were not associated with a change in visual function, as measured by clinical neuro-ophthalmologic examination. Our findings confirm the usefulness of VEPs in the detection of subclinical optic nerve disease and suggest their use in routine monitoring of ocular function in patients treated with ethambutol.

Somatosensory evoked responses in the diagnosis of thoracic outlet syndrome

A study was made of 11 patients with cervical rib, and one patient with Klippel-Fiel syndrome and enlarged transverse processes to determine whether evoked potentials recorded from both Erb's points and the cervical spine in response to median and ulnar nerve stimulation provided information additional to that obtained by EMG and peripheral conduction studies. It was found that in seven patients who had pain and paraesthesias but no objective neurological signs both the peripheral and central conduction studies were within normal limits. By contrast, of five patients who had objective signs, conventional EMG and conduction studies were abnormal in three patients, but abnormalities of the evoked potentials obtained from ulnar nerve stimulation were obtained in all five patients. It is suggested that this application of evoked potential estimation is a useful addition to the more conventional peripheral investigations.

Peripheral neuropathy associated with polycythemia vera

Nerve conduction studies were performed on 26 patients with polycythemia vera, 11 of whom had sensory symptoms in the extremities and 3 of whom had clinical signs of peripheral neuropathy. There was significant impairment of sensory conduction in the ulnar and sural nerves and mild slowing of motor conduction in the lateral popliteal nerve. Sural nerve biopsies were performed on three patients. The pathological findings, including teased fiber studies, were consistent with mild chronic axonal degeneration. There is an association between polycythemia vera and peripheral neuropathy.

Nitrofurantoin neuropathy

Four cases of severe peripheral neuropathy directly attributable to nitrofurantoin are reported. The neuropathy was not dose-related and not necessarily associated with abnormal renal function. Recovery was slow, and neither severity nor recovery was related to the total dose of the drug. The pathological changes seen on light microscopy and electron microscopy were those of acute, severe axonal degeneration. It is emphasised that nitrofurantoin is a neurotic drug and should not be prescribed to the elderly not to anyone with impairment of renal function.

Clinical evaluation of computed tomographic scanning

Computed tomographic (CT) head scans were performed on 100 patients in a neurology ward. The CT scan was diagnostic in 67 patients and suggestive in a further three patients. Computed tomographic scans were most likely to be diagnostic in patients whose symptoms at presentation could be classified as "traumatic intracranial lesion", "space-occupying lesion", "acute cerebrovascular lesion", "dementia", and "epileptic disorder", and much less likely to be diagnostic if a patient presented differently. In all cases where the CT scan was diagnostic. It was considered that, had a CT scan not been available, alternative tests such as nuclear scan, cerebral angiography or pneumoencephalogram (PEG) would have been performed and would also have been diagnostic; no impact of the CT scan on diagnosis, therapy or patient outcomes was documented. However, in patients who received a CT scan, there was a 91% reduction in the PEGs, 85% reduction in cerebral angiograms, a reduction of 73% in nuclear scans and 31% in electroencephalograms. Computed tomographic scanning costs no more than the tests it replaces in the clinical setting studied, and offers significant advantages in patient comfort and safety.