Narayan P. Verma

Electroencephalographic findings in Rett syndrome

Rett syndrome is a progressive neurologic condition, affecting only girls and characterized by acquired microcephaly, dementia, seizures, autistic behavior, spontaneous hyperventilation, spasticity, hyperreflexia and a peculiar characteristic stereotypic movement disorder. A review of 35 EEGs (obtained over 0-8.5 years of follow-up) in 9 such patients revealed a striking age-related change in the electroencephalographic pattern. Often initially normal, the EEG shows a variety of epileptiform abnormalities but intact background activity between 3 and 5 years. Between 5 and 10 years of age, the background activity exhibits some slowing, epileptiform abnormalities persist and paroxysmal high-amplitude theta activity occurs over extended periods, related to spontaneous hyperventilation. After 10 years, there is a general reduction in the epileptiform activity but further slowing of the background rhythms is usually observed. As all other laboratory tests are mostly normal in Rett syndrome, EEG promises to be a powerful tool in confirming the diagnosis in a compatible setting, in follow-up of these patients, and in objective evaluation of any future therapeutic interventional modalities in this serious and common condition.

Rett syndrome — a gray matter disease? Electrophysiologic evidence

Electrophysiologic dichotomy of abnormal EEGs, as reported by us previously, and normal evoked potentials, as reported in this communication, in patients with Rett syndrome, suggests a predominant gray matter pathophysiologic insult in this serious condition of unknown etiology.

Electroencephalographic findings in unmedicated, neurologically and intellectually intact tourette syndrome patients

Electroencephalograms were obtained in 30 unmedicated, neurologically and intellectually intact Tourette syndrome (TS) patients, none having a history of clinically apparent seizure disorder. Six (20%) of initial 30 EEGs were judged to be abnormal, 2 (6.6%) on account of slowing of intrinsic rhythms and/or excess of slow frequencies and 4 (13.3%) on account of epileptiform alterations. Two of the latter 4 patients continued to show similar abnormalities in EEGs done 4 and 8 months later. Five of 6 patients with abnormal EEGs had history of migraine or migraine equivalents compared to 8 of 24 with normal EEGs (chi 2 = 4.88, P less than 0.05). It is concluded that in the population of Tourette patients studied, EEG abnormalities occurred in one-fifth of all patients despite an absence of medication effect, brain damage or seizure disorder and may, in part at least, be related to associated migrainous equivalents.

Waves earlier than P3 are more informative in putative subcortical Dementias: A study with mapping and neuropsychological techniques

SummaryThirty subjects (normal controls, patients with putative subcortical dementia and non-demented patient controls) were studied using advanced neurophysiological (16 scalp-electrode positions, computer-assisted brain electrical activity mapping, auditory oddball paradigm) and neuropsychological techniques. Our study suggests that waves earlier than P3 (N1, P2 and N2) are all correlated with global measures of cognitive functions. They are, however, differentially correlated with specific measures of cognitive functions, N1 and P2 with mental speed and N2 with short-term memory. The abnormalities of these waves (earlier than P3) may be an electrophysiologic marker of dementia in patients with putative subcortical states.

Electrophysiologic studies in neonatal adrenoleukodystrophy

Recent electrophysiologic studies have focussed attention on the X-linked adrenoleukodystrophy (ALD) and its myeloneuropathic variant. No organized studies are, however, yet available on its relatively recently described neonatal variant. We conducted electroencephalographic, electroretinographic and evoked response studies in 2 patients with neonatal ALD. In one patient, an infant, initial EEG, hypsarrhythmic in waking and somewhat periodic in sleep, showed dramatic improvement on ACTH therapy accompanied with a seizure-free status. The EEG and clinical improvement, however, were temporary. No improvement occurred following pyridoxine therapy. Her electroretinogram (ERG), visual evoked responses (VERs) and far-field short latency brain-stem auditory evoked responses were also abnormal. The latter studies probably reflected photoreceptor degeneration, optic nerve involvement, cochlear and/or auditory nerve involvement respectively in neonatal ALD. The other patient, a 3.5-year-old girl, also had an EEG characterized by a moderate- to high-amplitude slow background activity and high-amplitude multifocal, generalized or periodic paroxysmal discharges, but presence of some better formed theta frequencies in background activity precluded a hypsarrhythmic label on her EEG. Her ERGs and VERs were totally extinct but in contrast to the first patient, she had clear-cut optic atrophy and retinitis pigmentosa on ophthalmological examination.

Periodic Lateralized Epileptiform Discharges in Acquired Immunodeficiency Syndrome

A patient with AIDS, who exhibited periodic lateralized epileptiform discharges, is described. The possible implications are discussed.

Dose-Response Effects of Chronic Methylphenidate Administration on Late Event-Related Potentials in Attention Deficit Disorder

Stimulants, such as methylphenidate, are extensively used in the treatment of attention deficit disorder. In the present study, we used a double-blind placebo-controlled, prospective protocol to evaluate the effects of methylphenidate (MP) (dose 0.1 and 0.33 mg/kg three times daily) on the late event-related potentials, some of which are considered biological attention correlates. Sixteen patients, 6-15 years old, were tested, using an auditory target selection paradigm. The latencies of N200 and amplitudes of P150 increased with MP (p less than 0.01). These effects are in the direction of normal maturational change. The latencies of P300 tended to be shorter in adolescents than in children, and with high MP dose the P300 latencies became even shorter in adolescents but were prolonged in children (p less than 0.05). This pattern of change supports the view that pharmacological interactions with various cerebral phenomena including cognition may be age-specific.

Sensory evoked responses in Tourette syndrome

Based on an earlier study of EEGs and the present article on sensory evoked responses, with a total of 32 patients, it appears that routine electrophysiologic studies do not provide a good biological marker in Tourette Syndrome.

An assessment of the variability of early scalp-components of the somatosensory evoked response in uncomplicated, unshunted carotid endarterectomy.

Although many publications deal with the usefulness of the SER in CEAs, the criteria of calling a SER abnormal during a CEA are largely arbitrary. One way to define the limits of normalcy for SERs during the CEA will be to analyze the SER tracings obtained during unshunted and uncomplicated (intra- and postoperative) CEAs. In 23 such CEAs (10 right, 13 left; clamptime 10-23 mins.), data analysis at the ipsilateral parietal electrode, on stimulation of the contralateral median nerve (square pulse -5.1/sec, 10-30 V, 200 microseconds; bandpass-30-3000 Hz trials-500 stimuli), revealed that (1) latency fluctuations of the N20 (21.4 msec) were narrowest, being less than 1.5 msec different during and after clamping compared to the preclamp latency in all 23 CEAs, whereas those of P25 (27.4 msec) and N35 (38.5 msec) were greater than 2.0 msec different from the preclamp latency in 3 and 8 CEAs respectively, and (2) the amplitudes of N20, P25 and N35 measured from the preceding peak of opposite polarity, fell to less than 75% of the preclamp value on 3, 4 and 7 CEAs respectively. It is concluded that N20 was the most stable of the first three short-latency components in the SER and should perhaps be most relied upon to predict abnormality of the SER during CEAs.

Gender factor in longer P100 latency of elderly persons

Monocular pattern-shift visual evoked potentials (PSVEPs) were obtained in 26 neurologically and ophthalmologically normal elderly community volunteers (mean age 59.4, males 15, females 11), and compared with similarly obtained data in 26 sex-matched young subjects (mean age 28.1). Elderly males were age-matched with elderly females, and young males were age-matched with young females. Data analyses at both the midoccipital-linked ears and midoccipital-midcentral derivations revealed that the combined-eye mean P100 latency in the elderly as a whole was significantly longer than the young sex-matched controls (P less than 0.02). However, the latency in the elderly males was not significantly different from that of sex-matched young males, or age-matched elderly females. The latency in young female subjects, on the other hand, was significantly shorter both when compared to that of age-matched young males (P less than 0.01) and sex-matched elderly females (P less than 0.01). The differences in other PSVEP variables, namely, interocular P100 latency differences, P100 amplitudes and interocular P100 amplitude ratios were not significant between the groups and subgroups studied. It is concluded that females account for the major contribution towards the longer P100 latency in the elderly.