Tablet-based electroencephalography diagnostics for patients with epilepsy in the West African Republic of Guinea.

BACKGROUND AND PURPOSE: Epilepsy is most common in lower-income settings where access to electroencephalography (EEG) is generally poor. A low-cost tablet-based EEG device may be valuable, but the quality and reproducibility of the EEG output are not established. METHODS: Tablet-based EEG was deployed in a heterogeneous epilepsy cohort in the Republic of Guinea (2018-2019), consisting of a tablet wirelessly connected to a 14-electrode cap. Participants underwent EEG twice (EEG1 and EEG2), separated by a variable time interval. Recordings were scored remotely by experts in clinical neurophysiology as to data quality and clinical utility. RESULTS: There were 149 participants (41% female; median age 17.9 years; 66.6% ≤21 years of age; mean seizures per month 5.7 ± SD 15.5). The mean duration of EEG1 was 53 ± 12.3 min and that of EEG2 was 29.6 ± 12.8 min. The mean quality scores of EEG1 and EEG2 were 6.4 [range, 1 (low) to 10 (high); both medians 7.0]. A total of 44 (29.5%) participants had epileptiform discharges (EDs) at EEG1 and 25 (16.8%) had EDs at EEG2. EDs were focal/multifocal (rather than generalized) in 70.1% of EEG1 and 72.5% of EEG2 interpretations. A total of 39 (26.2%) were recommended for neuroimaging after EEG1 and 22 (14.8%) after EEG2. Of participants without EDs at EEG1 (n = 53, 55.8%), seven (13.2%) had EDs at EEG2. Of participants with detectable EDs on EEG1 (n = 23, 24.2%), 12 (52.1%) did not have EDs at EEG2. CONCLUSIONS: Tablet-based EEG had a reproducible quality level on repeat testing and was useful for the detection of EDs. The incremental yield of a second EEG in this setting was ~13%. The need for neuroimaging access was evident.

Central nervous system amplification: its potential in the diagnosis of early multiple sclerosis.

Ability to record a sizable somatosensory evoked potential (SEP) in the absence of a recordable sensory nerve action potential (SNAP) suggests a normally occurring central nervous system amplifying process. Increments in SEP and SNAP amplitude with increasing stimulus strength between threshold and 2.5 times threshold (maximum) were compared. A threshold (40% of maximum stimulus) and 50% maximum stimulus, amplification measured 2.3 +/- 0.7 and 2.0 +/- 0.6, respectively. In 21 MS patients, the SEP at threshold stimulation was absent in 15, but normal in 5 of these at maximum stimulation. It is postulated that normal central amplification is markedly attenuated in MS, and this may be a sensitive indicator of early disease.

An epileptic syndrome caused by mesial frontal lobe seizure foci.

We describe an epileptic syndrome of bilaterally coordinated limb movements, axial movements, vocalization, and nonmasticatory oral activity. EEG and physiologic evidence indicates the syndrome is caused by ictal discharge in the mesial frontal lobes. Two of 12 patients were not helped by anterior temporal lobectomy, and 3 others improved after section of the anterior two-thirds of the corpus callosum.

Results of anterior corpus callosum section in 24 patients with medically intractable seizures.

Twenty-four medically refractory seizure patients, who did not qualify for excisional surgery, had anterior two-thirds corpus callosum section. Three to 11 years' postoperative follow-up suggests that this procedure can (1) lateralize a frontal lobe focus, which may lead to subsequent localized excision and (2) significantly reduce seizure frequency and severity in 75% of the patients without giving any permanent neurologic deficits. Patients with an ictal focus confined to one frontal lobe did best (8/8 improved), followed by patients with secondarily generalized seizures and multifocal bilateral foci (5/6 improved). Patients with mental retardation benefited less frequently (5/10 improved), but 4/4 from this group with ictal falls associated with Lennox-Gastaut syndrome did benefit. In this series, the improvements following the anterior partial section were lasting if present at 1 year of follow-up. Anterior corpus callosum section should be considered as a diagnostic (lateralizing) and therapeutic option in appropriately defined medically refractory patients who do not qualify for excisional surgery.

MRI in the diagnosis of MS: a prospective study with comparison of clinical evaluation, evoked potentials, oligoclonal banding, and CT.

We compared the diagnostic capabilities of MRI to CT, evoked potentials (EP), and CSF oligoclonal banding analysis in a prospective evaluation of 200 patients with suspected multiple sclerosis (MS). MRI was the best method for demonstrating dissemination in space. An abnormal appropriate EP in monosymptomatic disease was usually supported by MRI and CSF analysis as being predictive of MS as a clinical diagnosis. A normal appropriate EP study was not satisfactory because MRI and CSF analysis often did not support a diagnosis of non-MS. When there is agreement between three of these paraclinical studies, the diagnosis of MS is probably unequivocal. For use in research studies, laboratory-supported definite MS (LSDMS) could be diagnosed in 85 patients of the total 200 (42.5%), in 19/38 (50%) of optic neuritis (ON) patients, and in 24/52 (46%) of chronic progressive myelopathy (CPM) patients. MRI was 100% successful in identifying patients who qualified for LSDMS in the ON and CPM groups. In a short follow-up (less than 1 year), 19/200 (10%) went on to develop clinically definite MS (CDMS), and MRI predicted that diagnosis in 18/19 (95%). Only long-term follow-up will show how well these studies and the category of LSDMS predict the development of CDMS. The clinical diagnosis of MS (CDMS), even though only 95% accurate, must remain the gold standard.

Dual task performance by patients with left or right speech dominance as determined by carotid amytal tests.

Patients who had their speech dominance determined by carotid Amytal testing were evaluated with a dual task procedure consisting of reading and finger tapping. As expected, the asymmetry of interference between tasks varied with speech dominance. Patients with left hemisphere speech tended to show greater interference in the right hand whereas patients with right hemisphere speech showed greater interference in the left hand. Since the right hemisphere dominant patients were also right-handed, the results suggest that interference effects are more closely linked to speech than to motor dominance.

Occult fifth nerve dysfunction in multiple sclerosis.

Somatosensory evoked potentials (SEPs) were recorded following trigeminal nerve stimulation in 25 normal subjects. Mucosal stimulation of the lip resulted in a reduced stimulus artefact. The three initial peaks, N13, P19, and N30, measured respectively 12.8 +/- 0.9 S-3, 19.3 +/- 1.4 S-3, and 28.6 +/- 1.7 S-3. Blink reflex studies were also performed in most of these subjects. In 41.4% of 29 patients with established or suspected multiple sclerosis, the trigeminal SEP was abnormal. Additional use of the blink reflex raised the overall incidence of trigeminal nerve dysfunction to 51.7%. None of the patients had clinical evidence of fifth nerve involvement either historically or on examination. Four of seven patients with progressive spinal MS and two patients whose only deficit was that of optic neuritis, had abnormal trigeminal SEPs. It is concluded that occult involvement of the pontine fifth nerve structures occurs frequently in MS despite the rarity of corresponding clinical findings. The trigeminal SEP is a useful additional neurophysiological method.

A comparison of visual, brainstem auditory, and somatosensory evoked potentials in multiple sclerosis.

Multimodality evoked potentials testing including PVEPs, SEPs and BAEPs was done in 112 patients who were known or suspected to have multiple sclerosis. The incidence of abnormal evoked potential findings in each of these systems was considered in patients in the different diagnostic categories of M.S. Results were also evaluated with respect to the presence of abnormal clinical visual, somatosensory, or brainstem signs. The PVEP was found to be the most frequently abnormal in even patients without clinical involvement in the visual system (45% of patients with definite, probable, or possible M.S.), the SEP was less frequently abnormal in the absence of clinical signs (35% in patients with M.S.), and the BAEP showed the lowest frequency of abnormalities in patients without brainstem signs (14% in patients with M.S.). Combining the three types of evoked potentials significantly increased the percentage of M.S. patients having abnormal findings, compared to any of these tests alone, with 97% of "definite" M.S. patients, 86% of "probable" M.S. patients and 63% of "possible" M.S. patients having at least one of these EP tests abnormal.

Diagnosis of seizure disorders.

The author addresses the diagnosis of seizure disorders by discussing clinical features of the different types of seizures, including generalized tonic-clonic, absence, myoclonic, partial complex seizures, and non-epileptic or "pseudoseizures." She also discusses the use of appropriate laboratory tests, electroencephalography, computed tomography, magnetic resonance imaging, and positron emission tomographic scanning. The rationale of and approach to treatment of these conditions with some of the common anticonvulsant drugs (phenytoin, carbamazepine, valproic acid, phenobarbital, and primidone) is provided.

Improving the validity of clinical exercise testing: the relationship between practice and performance.

Many studies involving exercise testing fail to address the issue of practice. Those that do vary considerably with respect to the parameters of practice used. We evaluated the effect of two standardized practices on a horizontal submaximal exercise test performed on a treadmill. Healthy men (n = 20) with no previous treadmill exposure were alternately assigned to the experimental (practice) or control (no practice) group. Heart rate (HR), systolic blood pressure (SBP), rate pressure product (RPP), step cadence (CAD) and perceived exertion (PE) were recorded at the end of each work load of the practices and/or tests. We observed no significant differences in these variables over the common work loads for the first practice session in the experimental group and the exercise test in the control group (p greater than 0.05). The two groups were homogeneous with respect to fitness and magnitude of arousal on initial exposure to the treadmill. During the submaximal test, HR, SBP, RPP, CAD, and PE were systematically lower for the experimental group than for the control group. The SBP and RPP were significantly lower in the experimental group (p less than 0.01). The CAD tended toward statistical significance (p less than 0.07), whereas HR and PE were not significantly different for the two groups (p greater than 0.05). When the four common work loads were compared over the two practices and the exercise test for the experimental group, SBP and CAD were significantly higher for practice 1 than for practice 2 and the test (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral evoked potentials: a historical review of the marseilles contributions and a preliminary report on a study of the effects of various stimulus parameters on the P90 component of the pattern visual evoked potential.

A preliminary report is given of a study in 10 normal subjects comparing the laterality of the P90 component of the PVEP as elicited by pattern reversal and pattern appearance stimuli delivered monocularly and binocularly in the central and peripheral portions of one-life field. P90 was shown often to appear maximally over the hemisphere ipsilateral to the stimulus field with pattern reversal stimuli in central targets viewed monocularly. Pattern appearance, peripheral targets and binocular stimulation provoked less consistently lateralized and sometimes differently configured responses. It is concluded that while all combinations provoked responses consistent with a dipole generator model similar to that proposed by Blumhardt et al. (1978), these different modes of stimulation cannot be considered to be equivalent.