Age-related changes in peripheral and central nerve conduction in man.

Somatosensory evoked potential (SEP) latencies, motor and sensory nerve conduction velocities (CVs), and F-wave latenies were measured in 15 elderly normal subjects (mean age 74.1 years), and the results were used to derive indirect estimates of spinal cord CVs. These measurements were compared to those from 15 younger normal adults (mean age 31.6 years), and the nerve conduction characteristics of all 30 subjects were analyzed with respect to age. Peripheral motor and sensory CVs slowed progressively, and the onset latencies of F-waves and SEPs increased gradually with advancing age. Spinal cord CVs showed little change until approximately age 60, and declined sharply thereafter. In addition, the latencies of F-waves and SEPs were positively associated with height. Human clinical and experimental studies utilizing SEP and F-wave measurements must allow for morphologic differences between individuals, and for the systematic changes which accompany normal aging.

Spinal somatosensory conduction in diabetes.

The velocity of impulse conduction was compared in peripheral nerve, spinal cord, and supraspinal segment of the somatosensory pathway in 15 diabetic subjects (mean age, 34.3 +/- 12.4 years) with little or no evidence of polyneuropathy, and in 15 age-matched normal controls. Motor and sensory conduction velocities (CVs) were slower in the diabetic subjects, and the latencies of F waves and somatosensory evoked potentials (SEPs) from arm and leg were longer (p less than 0.001 in each case), showing a relationship to duration of disease (0.51 less than lrl less than 0.84, p less than 0.001 in each case). Indirect estimates of spinal somatosensory conduction velocity (SSCV) were slower in the diabetic subjects (39.4 +/- 13.3 m/sec versus 54.2 +/- 10.5 m/sec, p less than 0.001), but conduction in the supraspinal segment (cervical cord to cortex) was identical in the two groups (5.6 +/- 1.3 msec versus 5.6 +/- 0.8 msec, p less than 0.1). In relationship to peripheral nerve CV, the incidence of subnormal SSCV in the diabetic subjects could not be fully explained on the basis of: (1) a passive consequence of peripheral neuropathy, (2) a sensory distal axonopathy, or (3) a primary diabetic myelopathy. We conclude that 40% of diabetics have subclinical electrophysiologic dysfunction of the posterior columns of the spinal cord, which may contribute to the lower-extremity sensory symptoms that are so prevalent in this disorder.

Cerebral infarction and migraine: clinical and radiologic correlations.

Cerebral infarction was documented by arteriography and serial computed cranial tomography (CT) in four young adults (ages 16 to 32 years) with migraine. In one case, posterior cerebral artery occlusion produced a deep parietotemporal infarct. The other three cases all had frontotemporal infarcts (one hemorrhagic) in the territory of the middle cerebral artery, without major arterial occlusion. Two infarcts produced lasting neurologic deficits; one was associated with mild, transitory symptoms, and one was asymtomatic. Laboratory investigations in two cases revealed no hematologic or cardiovascular predisposition to cerebrovascular disease. Cerebral infarction, as revealed by CT, may be more prevalent in "complicated" migraine than is generally appreciated. Such lesions may or may not develop in chronologic and anatomic relationship to the headache, and may involve either large or small arteries. The prognosis for functional recovery, based on this limited sample, seems favorable.

"Encephalomyeloneuritis" in the absence of cancer.

An elderly man presented with signs and symptoms indicating a rapidly progressive central and peripheral nervous system disease, which led to death within 3 months. The pathologic picture was that of a "paraneoplastic" encephalomyelitis and neuritis, but no cancer could be found. Supratentorial predilection for the limbic structures correlated well with an observed limbic dementia. Arguments favoring a direct toxic or metabolic effect of cancer as a cause for this syndrome was less convincing in view of this report.

Visual electrical evoked potentials: evaluation of ocular injuries.

Clinical neurophysiologists may be asked to participate in the evaluation of patients with injured eyes. We describe a method for eliciting evoked potentials of cerebral origin using electrical pulse stimuli delivered to the globe of the eye through a contact lens electrode mounted on the cornea. These visual electrical evoked potentials (VEEPs) are contrasted with conventional flash visual evoked potentials in normal subjects and in 19 eyes of 17 patients with severe ocular damage, mostly recent trauma. The findings suggest that the site of transcorneal electrical excitation is not the photoreceptors, but more likely one of the nerve cell layers of the retina. VEEP recordings offer a way to circumvent the opacification of the ocular media by blood, which may otherwise hamper the evaluation of retinal function in the injured eye. Preserved VEEP response does not necessarily predict the capacity to recover visual function. Absent VEEP response is an unfavorable prognostic sign, which may be considered in arriving at a decision about enucleation.

Studies of diabetic polyneuropathy using conduction velocity distribution (DCV) analysis.

The distributions of nerve fiber conduction velocities (DCVs) derived from the median nerves of 29 adult diabetic patients (mean age, 52.1 +/- 12.3 years) with mild or no symptoms or signs of polyneuropathy were compared with DCVs from 34 age-appropriate normal subjects. Ten patients (34%) had normal findings (type A DCVs). In the 19 patients (66%) with abnormal DCVs, defined as 10% or more of the DCV area falling outside the normal 95% confidence limits, two distinct patterns of DCV alteration were observed: type B DCVs (11 patients) showed reduced DCVmax, DCVmean, and DCVpeak, together with reduced DCVrange (narrow profile); whereas type C DCVs (8 patients) had reduced DCVmax, DCVmean, DCVpeak, and DCVmin, with normal DCVrange (broad profile). It is proposed that type C DCV represents a more advanced form of type B and that both reflect selective dysfunction of the fastest conducting (presumably largest-diameter) fibers in the nerve trunk. DCVmax was consistently greater than conventional measures of "maximal" CV in all patient subgroups. Patients with abnormal DCVs had higher incidence of mild neuropathic symptoms (15 of 19 versus 4 of 10, p less than 0.01) and greater insulin dependence (11 of 19 versus 1 of 10, p less than 0.001). Serial studies in 10 patients showed, at most, small degrees of change in conduction properties over relatively short intervals (1 to 9 months).

Leber's disease and dystonia: a mitochondrial disease.

We studied a kindred in which 8 members had the neuroretinopathy of Leber's disease; 14 had a progressive, generalized dystonia attributed to striatal degeneration; and 1 had both disorders. The mode of inheritance was compatible with maternal transmission. This neurologic disorder may be a mitochondrial disease.

The early phase in Leber hereditary optic atrophy.

Clinical, ophthalmoscopic, perimetric, and color vision tests and visual evoked responses were recorded in symptomatic and asymptomatic eyes in five members of a family with Leber hereditary optic atrophy. The presymptomatic eyes showed abnormalities in the retinal nerve fiber layer. Optic nerve dysfunction was found before central vision failed. The appearance of degenerating retinal nerve fibers, particularly in the papillomacular bundle, was documented photographically in the weeks after the onset of visual symptoms. Treatment with prednisone and hydroxocobalamin did not reverse or halt serious impairment of vision.

Influence of contractile force on properties of motor unit action potentials: ADEMG analysis.

We have used automatic decomposition electromyography (ADEMG) to measure the configurational and firing properties of 13,206 motor unit action potentials (MUAPs) in the brachial biceps, brachial triceps and anterior tibial muscles of 30 healthy adults (22 men, 8 women; mean age 48.6 +/- 16.9 years, range 20-76) at three levels of isometric contractile force: threshold, 10% of maximum voluntary contraction (MVC), and 30% MVC. In all muscles, the increment in contractile force from threshold to 10% MVC was associated with a significant (P less than 0.05, paired t-test) increase in mean MUAP firing rate and number of turns per MUAP. The increment from 10% to 30% MVC led to highly significant (P less than 0.005) increase in mean firing rate, number of turns, amplitude and rise rate. Each force increment was associated with an increase in the number of simultaneously-active MUAPs per recording site; and with a significant decrease in mean MUAP duration in all muscles, due to noise-dependency of the duration measurement. Quantitatively, the changes in MUAP properties with force were comparable to or exceeded the effects of age, gender differences, or intermuscular variability. Test-retest measurements 2 years apart in a subgroup of young adults showed good correspondence of mean MUAP properties with force standardization. These results demonstrate that contractile force is a major determinant of MUAP shape and behavior properties, and so must be precisely measured or controlled in clinical EMG studies.

Neuroaxonal dystrophy (Seitelberger's disease) with late onset, protracted course and myoclonic epilepsy.

We present the pathologic findings, including electron microscopy, in one of two affected borthers with severe progressive myoclonus epilepsy, beginning in our patient at the age of 10 and leading to death at age 23. At autopsy there was widespread and marked neuroaxonal dystrophy, severe cerebellar atrophy, and tract degenerations in the gracilis columns and the lateral corticospinal tracts in the spinal cord. There was no increased pigmentation in the globus pallidus or reticular zone of the substantia nigra, on gross or microscopic examination. We regard this case as an example of a juvenile form of neuroaxonal dystrophy (Seitelberger's disease). The absence of pallido-nigral hyperpigmentation distinguishes this disease from Hallervorden-Spatz disease, which we regard as a separate disease entity.

Traumatic lesions of pontomedullary junction.

An autopsied series of 162 consecutive fatal head injuries was analyzed for location and type of primary brain stem injury. Of 41 cases with primary brain stem injury, 24 (59%) demonstrated 22 tears and 2 complete transections at the level of the pontomedullary junction. Three cases are presented in detail to illustrate the range of structural and functional damage seen with trauma at this level of the brain stem. A pathologically verified case of traumatic "locked-in" syndrome is reported, including serial brain stem auditory evoked responses that are correlated with the neuropathological findings. In addition, two cases of primary traumatic damage at the pontomedullary junction (one tear and one total transection) are described; these were associated with instantaneous death at the time of injury. Pathophysiologically, the tearing or disruption occurring at this level results from rapid hyperextension, which produces stretching at the pontomedullary junction.

Evoked potentials in hysteria and malingering.

Evoked potentials are often helpful in confirming the nonorganic nature of sensory symptoms in hysteria and malingering. In a retrospective analysis, such cases were found to comprise approximately 1% of referrals to a university hospital laboratory. However, the diagnostic usefulness of electrophysiologic tests is limited in some clinical settings: normal responses may be encountered in subjects with certain organic deficits, and "abnormal" responses can sometimes be produced voluntarily by normal subjects. In malingering--as opposed to hysteria--the role of the technologist in monitoring patient compliance with the test procedure is particularly important. Like other laboratory investigations, evoked potential findings must be interpreted within the context of each clinical situation, and with full appreciation of the sensitivities and specificities of the tests.

Use of cerebral evoked potentials to evaluate spinal somatosensory function in patients with traumatic and surgical myelopathies.

Cerebral somatosensory evoked potentials (SEP's) were elicited by electrical stimulation of the median nerve in the arm (SEPA) and of the posterior tibial nerve in the leg (SEPL) in 23 patients with incomplete localized lesions (including traumatic injuries, neoplasms, vascular malformations and infarcts) of the low cervical, thoracic, or lumbar spinal cord. In eight of 46 attempts (left and right sides), SEPL could not be recorded. Of the remaining 38 sides, spinal somatosensory conduction velocity (SSCV, indirectly estimated) was abnormally slow (less than 35 m/sec) in 20, and the amplitude of SEPL relative to SEPA (L:A ratio) was abnormally low (less than 0.5) in 20 (p less than 0.001 in each case, compared to normal controls). All three criteria yielded a combined 72% incidence of abnormality, correlating best with impairment of joint position sense. Serial postoperative studies in four cases documented an increase in the SSCV and L:A ratio following spinal decompression. These results demonstrate that the latency and amplitude characteristics of the cerebral SEP's from arm and leg permit quantitative evaluation of the functional status of the spinal somatosensory system.

Neuroradiologic correlates of cognitive impairment in adult Moyamoya disease.

BACKGROUND AND PURPOSE: MMD has been shown to result in impairment of executive functioning in adults. The purpose of this study was to correlate presurgical neuropsychological assessments with the severity of primary MMD as measured by CBF and CVR and with secondary damage from MMD as estimated by cortical stroke and WMD. MATERIALS AND METHODS: A retrospective analysis of 31 adult patients with MMD was performed. Xe-CT was used to obtain CBF and CVR, and MRI was reviewed to grade cortical stroke and WMD. Two tests of executive functioning (FAS and TMT-B) were correlated with imaging findings. A multiple regression analysis was performed. RESULTS: There was a significant overall positive relationship between mean CBF and FAS (P = .038) and TMT-B scores (P = .014). A significant negative relationship was present between the WMD score and the FAS (P = .009) and TMT-B scores (P = .015). Per-region analysis demonstrated that FAS and TMT-B scores were significantly decreased by the presence of a posterior stroke (P < .0001 and P = .001) or WMD (P = .006 and P = .004). All patients with posterior parieto-occipital WMD or stroke also had secondary disease in the anterior regions. CONCLUSIONS: Impaired executive functioning in adults with MMD is most strongly associated secondary damage in the form of WMD or cortical stroke. The effect is most profound with parieto-occipital lobe involvement, likely a reflection of overall disease severity. Increasing global WMD burden may be a better indicator of cognitive decline than cortical infarction. Patients with higher baseline CBF seem to have better cognitive functioning.