Patient Motivation for Laser in situ Keratomileusis in the State of Bihar

PURPOSE

To evaluate the main reasons for seeking laser in situ keratomileusis (LASIK) and patient satisfaction after surgery in the socioeconomically underdeveloped eastern state of Bihar, India.

METHODS

This retrospective study evaluated results of the first 100 consecutive patients (169 eyes) who had LASIK at our center from July 2002 to September 2003.

RESULTS

Of the 100 patients, 65% were male and 35% were female. Ninety percent of male patients were between 18 and 24 years old; they sought LASIK to achieve an uncorrected visual acuity of 6/6 to 6/9-the basic qualifying criterion for jobs in the railway and defense services. Eighty-six percent of female patients were of marrying age. At 1 month after LASIK, 93% of patients achieved an UCVA of 6/6, 4% had UCVA between 6/9 to 6/12, and only 1% had <6/60.

CONCLUSION

In the socioeconomically poor state of Bihar, the main reason for males in our study to seek LASIK was to enhance their job prospects. In females, the main reason was to improve facial appearance in order to enhance marriage prospects.

Hypoparathyroidism with extensive intracranial calcification: a case report

We present a case of hypoparathyroidism, demonstrating extensive intracranial calcification, not only in basal ganglia, but also outside the extrapyramidal system. The patient presented with an unexplained epileptifors disorder, accompanied by extrapyramidal dysfunction in the form of choreoathetosis and hemiballismus. Hemiballismus is reported for the first time to our knowledge in association with hypoparathyroidism.

Microalbuminuria in non insulin dependent diabetes and essential hypertension: a marker of severe disease

Sixty five (65) hypertensive, 91 non-insulin dependent diabetes and 50 matched, healthy controls were examined for the presence of microalbuminuria, using the Micral strip test. Microalbuminuria was observed in 25 per cent of diabetics and 21.54 per cent of hypertensive subjects. None of the controls demonstrated microalbuminuria. Diabetics with microalbuminuria were poorly controlled and demonstrated significantly higher systolic pressure. In hypertensive subjects, microalbuminuria was seen more in patients with severe disease. In both diabetics and hypertensives, presence of microalbuminuria was significantly influenced by the disease duration.

A study of hyperinsulinaemia in Indian hypertensive subjects

Fasting and 2 hours post-prandial serum insulin levels were estimated in 100 hypertensive subjects and 25 matched, healthy controls, by radio-immuno assay (RIA). Seventy four of the 100 hypertensives exhibited fasting hyperinsulinaemia. Post-prandial hyperinsulinaemia was present in 85 hypertensives. None of the healthy individuals demonstrated hyperinsulinaemia. Although, most hyperinsulinaemic patients exhibited an abnormal lipo-protein profile, there was no statistical correlation between absolute values of lipo-protein and insulin.

Differential but infrequent alterations of hepatic enzyme levels and thyroid hormone levels by anticonvulsant drugs

OBJECTIVE

To assess the differential effects of antiepileptic drugs (AEDs) on hepatic enzyme and thyroid hormone levels and to assess the frequency and degree of these alterations.

STUDY DESIGN

Retrospective analysis of hepatic enzyme (serum aspartate aminotransferase and alanine aminotransferase) and thyroid hormone (thyroxine, T uptake; and free thyroxine index) levels obtained during a 10-year period in a large unselected outpatient population of patients with epilepsy.

PATIENTS

Unselected (for age, sex, race, type of epilepsy, or degree of control) epileptic subjects (n = 642 for determination of hepatic enzyme levels and n = 317 for determination of thyroid hormone levels) attending the largest outpatient epilepsy center in the Midwest. Infants (younger than 1 year) and those receiving more than two AEDs were excluded.

OUTCOME MEASURE

Hepatic enzyme and thyroid hormone level alterations vis-à-vis the type of AED, serum AED levels, and monotherapy vs bitherapy.

RESULTS

Aspartate aminotransferase level alterations were mainly due to valproate or phenobarbital, and alanine aminotransferase alterations were due to phenytoin. Significant enzyme level elevations were infrequent (2% [14/642] of patients), mild, usually associated with bitherapy, transient, and confined to aspartate aminotransferase level. Persistent elevations of both aspartate aminotransferase and alanine aminotransferase levels occurred in only one patient, and he had underlying liver disease. Phenytoin was most and phenobarbital least likely to influence the thyroid indexes. Although bitherapy was more likely to produce biochemical alterations of thyroid hormone levels compared with monotherapy, clinically significant thyroid hormone level alterations were seen in only one of 317 patients, and this patient was known to have hypothyroidism.

CONCLUSIONS

Antiepileptic drugs affect hepatic enzyme and thyroid hormone levels differentially, and bitherapy alters them more than monotherapy does. However, alterations are mostly mild and clinically insignificant and do not justify routine testing, except in those known to have a coexisting hepatic or thyroid abnormality, those who develop symptoms of hepatic or thyroid involvement while receiving AEDs, and perhaps those receiving bitherapy with high serum AED levels.

Event-related potentials in complex partial seizures

Both early (N1 and P2) and late (N2 and P3) event-related potentials (ERP) were obtained in 16 patients with complex partial seizures, 12 with left hemispheric ictal focus and 4 with right, to see if they help in lateralizing the seizure focus, and also to determine if they correlate with behavioral (MMPI, Bear-Fedio), attentional (Trails A and B), cognitive (WAIS-R, Boston Naming, Warrington Word and Face recognition) and mental speed (Stroop color naming and reading) tasks. Early waves were more often lateralized than late waves but both were often falsely lateralizing. Early waves were better correlated with behavioral tasks whereas late waves were better with those measuring mental speed, attention and cognition. These data tentatively discourage the utility of ERP in preoperative lateralization of seizure focus but argue for their potential value in psychophysiological correlations.

Lateralizing value of transient hypofrontality during Wada's test

Five of 22 subjects who underwent Wada's test in our institution over last year developed transient hypofrontality, always following the injection of the side contralateral to seizure focus (as defined by prior ictal recordings). This event may have lateralizing value and could well be because of pharmacological ablation of contralateral frontal-lobe combined with compromised ipsilateral frontal-lobe causing transient hypofrontality.

Carbamazepine offers no psychotropic advantage over phenytoin in adult epileptic subjects

We compared 19 men on carbamazepine (CBZ) monotherapy with 19 men on phenytoin (PHT) monotherapy, all of whom had standard therapeutic levels. The two groups were matched for age, sex, education, premorbid predicted IQ, seizure frequency, duration, number, type and aetiology, weekly ethanol consumption and psychiatric history. The two groups did not differ statistically on self- and reliable-informant rated personality inventories, word recognition, face recognition, confrontation naming, finger oscillation or trailmaking series completion times. These data fail to support a behavioural and cognitive advantage of CBZ over PHT in adult epileptics.

Prior head injury accounts for the heterogeneity of the alcohol-epilepsy relationship

Fifty-five adult male patients with alcoholism and seizures were divided into three groups. In group I, all seizures were consistently produced by alcohol withdrawal (N = 16); in group II, some seizures were clearly precipitated by alcohol withdrawal and others were not (n = 18); and in group III none of the seizures had a consistent relationship with drinking (N = 21). The three groups were compared for age, frequency of seizures, compliance, Bear-Fedio and Boston-Naming scores, those for memory of words and faces, and finger-tapping scores, and neuropsychological impairment ratings as well as EEG background frequencies. The incidence of severe head injury preceding the onset of seizure disorder was significantly higher in groups II and III. This was further supported by a greater prevalence of asymmetric alpha rhythm, abnormal CT scans and multiple seizure types in those two groups. These data indicate that a prior head injury is a major variable accounting for the heterogeneity of the alcohol-epilepsy relationship.

Enalapril monotherapy in essential hypertension

Thirty adults with essential hypertension (systolic BP greater than 150 mmHg or diastolic BP greater than 100 mmHg) were treated with 5-20 mg of enalapril to study its anti-hypertensive efficacy and safety. Ten patients had mild hypertension (diastolic BP greater than 90 mmHg and less than 105 mmHg), 10 had moderate hypertension (diastolic BP greater than 105 mmHg and less than 115 mmHg) and 6 had severe hypertension (diastolic BP greater than 115 mmHg). Of the 20 patients who completed the trial, 9 (45%) showed optimum reduction of BP to less than 130/90 mmHg) and a further 7 (35%) showed significant reduction. The mean fall in systolic BP was 32.5 mmHg (0-80 mmHg) and in diastolic BP was 18.5 mmHg (0-50 mmHg). The peak fall in BP was achieved in 3.5 weeks (1-6 weeks) with a mean dose of 7.2 mg of enalapril daily (5-15 mg/day). Mild side effects not needing drug withdrawal were seen in 8/20 patients (40%). Monotherapy with enalapril appears to be effective and safe as step one therapy for patients with essential hypertension.

Plasma renin activity in diabetics with and without microangiopathy

Plasma renin activity was measured in ten diabetics with nephropathy, 10 uncomplicated diabetics and 10 normal healthy controls. All the groups were comparable for age, sex, and duration of diabetes. Plasma renin activity was found to be significantly lower in patients with nephropathy in comparison to uncomplicated diabetics and normal healthy controls. There was no correlation between plasma renin activity and mean blood pressure or degrees of renal failure. These findings raise the possibility that microangiopathic changes occurring in the glomeruli and juxta-glomerular apparatus may alter the renin-angiotensin system. Also the finding of low renin in diabetics with nephropathy may modify management policies.

Brain electrical activity mapping of monocular P100 reveals another type of uncrossed asymmetry

Reference-independent analysis of monocular full-field P100 reveals another type of uncrossed asymmetry, not hitherto appreciated, and perhaps dependent on skull-impedance characteristics.

Blood histaminase in phlyctenulosis

Blood Histaminase estimations were done in 42 cases of phlyctenulosis and 25 normal subjects. Significantly higher level of blood Histaminase was found in patients of phlyctenulosis, which may be a consequence of its induction secondary to increased release of histamine in the early phase of disease.

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

Thirty 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.

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.

Ear-to-ear derivation in short latency brainstem auditory evoked responses

We utilized an ipsilateral to contralateral earlobe (Ai-Ac) derivation in addition to the scalp to ipsilateral ear (Cz-Ai) and scalp to contralateral ear (Cz-Ac) derivations, in 12 normal hearing community volunteers and 36 patients with a variety of referrals and varying degrees of hearing loss. In normal subjects, the latency of wave I in the Ai-Ac derivation was identical to that in Cz-Ai, but amplitude was consistently smaller (0.21 +/- 0.1 vs. 0.30 +/- 0.13 microV, p less than 0.005). The wave III behaved in a reverse manner. These data can be easily explained based on traditional principles of near- and far-field potentials. The amplitude differences of the wave I in Cz-Ai and Ai-Ac derivations were, however, small and the phase-reversals of that wave between the 2 derivations were striking and consistent in all subjects and patients. This observation indicates that the addition of Ai-Ac derivation to the conventional 1 or 2 channel montage may aid in the identification of wave I.

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.

Pathogenesis of reduplicative paramnesia

The incidence of reduplicative paramnesia was sampled with a structured interview in 50 consecutive alcoholic inpatients. Four had reduplicative paramnesia (RP group) and 46 did not (non-RP group). Three of four patients in RP group had acute right hemispheric lesions and none had a left hemispheric lesion; 19 non-RP patients had left hemispheric lesions, 2 had right, and 25 had none. These data are in keeping with the previous suggestions that the neuroanatomical basis for reduplicative paramnesia is an acute right hemispheric lesion superimposed on chronic diffuse or bifrontal deficit.

Multimodality evoked potentials in sarcoidosis

Neurosarcoidosis is suspected on clinical grounds and then confirmed by radiography, by spinal fluid examination, or by biopsy. To determine whether evoked potential testing may also be of value in diagnosing and following the course of neurosarcoidosis, multimodality evoked potentials were obtained in 12 men with sarcoidosis, including two with neurosarcoidosis. Seven of 12 subjects, one of whom had neurosarcoidosis, manifested abnormal evoked potentials. Visual evoked potentials were abnormal in one patient and somatosensory evoked potentials were abnormal in one patient. Five additional patients, including one with neurosarcoidosis, had abnormal auditory evoked potentials suggestive of auditory nerve or low pons involvement. These data indicate that multimodality evoked potentials, especially auditory potentials, may show central nervous system involvement in patients with sarcoidosis in the absence of clinically apparent disease.

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.

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.

Multimodality evoked response testing in sarcoidosis

Neurosarcoidosis is suspected on clinical grounds. The diagnosis is confirmed radiographically or by spinal fluid examination or biopsy. Evoked response testing in sarcoidosis has been studied by three groups of investigators. Visual, somatosensory, or brainstem auditory evoked potentials were abnormal in some sarcoidosis patients with, and in others without clinical evidence of neurological involvement. Multimodality evoked response testing may be useful in further defining neurosarcoidosis and in detecting subclinical disease.

Bimodality electrophysiologic evaluation of brainstem in sleep apnea syndrome

Previous electrophysiologic studies in the sleep apnea syndrome (SAS) have used only a single modality (brainstem auditory evoked responses [BAERs]) and yielded conflicting, inconsistent, and inconclusive results. We utilized both BAERs and somatosensory evoked responses in 12 patients with SAS and found normal central conduction times in all patients. These data argue against a significant structural alteration in both rostral and caudal brainstem, insofar as the auditory and somatosensory pathways are concerned, in patients with SAS.

Electrophysiologic validation of two categories of dementias--cortical and subcortical

Recently, the dementias have been classified into 2 categories-Cortical (CD) and Subcortical (SD). Some studies have questioned this classification. We attempted to validate the classification on electrophysiologic grounds. Fourteen of 15 patients with SD had relatively normal EEGs as compared to only 3 of 15 patients with CD, matched for age, sex and severity of dementia (p greater than 0.01). SER test results were often abnormal in the SD group but always normal in CD patients. These preliminary data appear to validate the classification of dementias into SD and CD categories.

Periodic lateralized epileptiform discharges in a patient with definite multiple sclerosis

The occurrence of PLEDs is described in a patient with definite, long-standing multiple sclerosis and the rarity of such an association is emphasized.

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.

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.

Contralateral epileptiform transients in stroke (CETS)

Epileptiform discharges occurring either periodically (PLEDs) or nonperiodically ipsilateral to a cerebral infarction are well known. Also, bilateral independent periodic transients (BIPLEDs) can occur in strokes complicated by hypoxia and/or infection. We bring attention to an EEG event, not previously described to our knowledge, for which we propose the term "contralateral epileptiform transients in stroke (CETS)." This phenomenon is apparently rare and consists of nonperiodic spikes occurring singly and in bursts, sharp waves, or sharp-and-slow waves occurring contralaterally to an acute stroke. These discharges are unassociated with clinical seizure and appear to last longer than PLEDs or BIPLEDs. Sometimes, they may point to a contralateral cerebral and/or cardiac pathology.

Visual evoked response in head trauma: pattern-shift stimulus

Studies of visual evoked potentials in head injuries have all utilized the flash stimulus. We studied the efficacy of monocular pattern-shift visual evoked potentials (PSVEPs) in eliciting residual dysfunction of the visual pathways in 33 patients 6 to 24 months after head injury. Those with ocular trauma or ocular pathology were not included. Abnormal PSVEPs were seen in one-third of 33 head-injured patients. Only 1 (11%) of 9 patients with mild cognitive impairment had abnormal PSVEPs compared with 7 (39%) of 18 with moderate and 3 (50%) of 6 with severe cognitive impairment.

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.

'Normal' and 'abnormal' crossed asymmetry in monocular visual evoked potentials

To restate the above, in the population of 29 normal subjects tested by us, 'normal' crossed asymmetry occurred in one-fifth on the FVEP study and in none on the PSVEP study; this 'normal' crossed asymmetry was always undirectional, larger Wave III being contralateral to the stimulated eye. Deviations from these observations, namely a larger Wave III ipsilateral to the stimulated eye, or a crossed asymmetry of P100 on the PSVEP study are probably examples of 'abnormal' crossed asymmetries. However, a 'normal' crossed asymmetry may occur in some abnormal situations as well, e.g. diseases and syndromes with optic misrouting as noted earlier.

Auditory evoked responses in multiple sclerosis. Wave I abnormality

Far-field short latency auditory evoked potentials (AEPs) were obtained in 40 patients with definite multiple sclerosis (MS) and 20 normal control subjects. Nine of 40 patients had abnormal wave I and normal hearing as established by pure tone audiometry. It is concluded that, in the population of patients with MS tested, slightly more than one fifth had AEP evidence of subclinical involvement of the auditory portion of the eighth cranial nerve.

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.

Monocular pattern-shift visual evoked potentials in hemispheric strokes

Monocular pattern-shift visual evoked potentials were obtained in (i) 33 patients with unilateral non-hemorrhagic hemispheric infarction (age 50-79 years; 23 males, 10 females), (ii) 21 age- and sex-matched patient controls (control group or CGI) with no remote or recent stroke, normal neurological examination and similar incidence of diabetes mellitus, hypertension and heart disease, and (iii) 21 age- and sex-matched healthy elderly community volunteers (CGII). Subjects with history of glaucoma, cataracts, other media opacities or symptomatic retinal lesions were not considered or included in any of the 3 study groups. In addition, all subjects in each of the 3 groups had a normal ocular and fundoscopic examination. The mean interocular P100 latency difference in the stroke group was significantly greater than that in CGI or II (P less than 0.01). The mean interocular P100 amplitude ratio (small P100/large P100) in the stroke subjects was significantly different from that of CGI or II (P less than 0.02). The mean P100 latency on ocular stimulation ipsilateral to the side of infarction was significantly longer than that of either left or right ocular stimulation in CGI or II (P less than 0.01). The mean P100 latency on ocular stimulation contralateral to the side of infarction was similarly but less significantly longer than that on left or right ocular stimulation in CGI or II (P less than 0.05). Evidence of anterior visual pathway dysfunction was thus elicited in the stroke population using the technique.

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.