1. Refractory Multifocal Epilepsy and Reflexly-evoked Giant Cortical Potentials: Reflex Simple Partial Seizures or Cortical Reflex Myoclonus? A Case Report. A.K. Chattopadhyay1, P.G. Sarrigiannis1, J. Fotheringham1 and S.R. Mordekar2. (1Royal Hallamshire Hospital, Sheffield, and 2Sheffield Children’s Hospital, Sheffield, UK).
A 13 year boy presented with frequent clinical attacks involving the left foot. Initially there was tonic/dystonic contraction of the foot which was followed by repetitive twitching. The ictal EEG showed focal epileptiform activity confirming simple partial seizures. The interictal EEG showed posterior multifocal sharp waves (left > right). Repetitive tapping of the left foot evoked a giant (58 µV) cortical waveform at the vertex which preceded a reflexly-evoked myoclonic jerk of the same leg, revealed by back-averaging. The somatosensory evoked potential (SEP) had a large amplitude and electrical stimulation of the right posterior tibial nerve triggered a focal seizure with secondary generalisation. The past history included other focal seizure types like left-sided tonic evolving to tonic-clonic seizures or periods of elementary visual hallucinations (flashing lights).
These findings are consistent with a hyperexcitable cortex giving rise to refractory focal seizures. Giant SEPs and long latency reflexes are usual findings in cortical reflex myoclonus. This child has a form of reflex epilepsy. Whether the present seizures are reflex simple partial seizures or reflex cortical myoclonus is debatable.
2. The EEG in Carbamazepine Toxicity: Two Illustrative Cases and Literature Review. S. Bazir-Ahmad, N. Kane and K. Sieradzan. (Grey Walter Department of Clinical Neurophysiology, Frenchay Hospital, Bristol, UK).
Carbamazepine is traditionally the drug of first choice in the treatment of simple and complex partial seizures and trigeminal/glossopharyngeal neuralgias. The symptoms of carbamazepine (5H dibenzazepine 5 carboxamide) toxicity include drowsiness, slurred speech, ataxia, hallucinations, nausea, vomiting, tremors and seizures. We encountered two female patients (49 and 68 years old), one being treated for neuropathic pain and the other for complex partial seizures, who both presented with intermittent speech disturbance, one with intermittent ataxia and the other in a confusional state. Both were found to have toxic levels of carbamazepine and quite characteristic EEGs in the acute episode. The EEGs were slow, with frontal intermittent rhythmic delta like activity (FIRDA). The patients were both treated by cessation of their carbamazepine, which led to resolution of symptoms and ‘normalisation’ of their EEGs. It is thus worth bearing in mind that carbamazepine is a neurotoxic drug and, although perhaps less common than that associated with phenytoin or valproate, the possibility of carbamazepine toxicity should be entertained in a patient presenting with encephalopathy and a FIRDA-like EEG.
3. QTc Measurement in EEG: Is this in the Neurophysiologist’s Domain? R. Jain, R. Kennett and R. Knight. (Department of Clinical Neurophysiology, John Radcliffe Hospital, Oxford. UK).
Objective: Young people referred for EEG recording following loss of consciousness may have cardiac arrhythmia due to prolonged QT interval. We performed this study to determine whether ECG recordings made during standard EEG tests are reliable to detect QTc abnormalities.
Methodology: QTc interval was calculated by Bazett’s formula in 100 random prospective EEGs in wake state. It was calculated in lead I in 50 patients and in both leads I and II in another 50 patients to detect ease and accuracy of measurement. All abnormal QTc intervals in EEG recordings were then cross-checked in 12 lead ECGs.
Results: QTc intervals were easy to measure and similar in both lead I and II of the EEG recordings. Six patients were identified to have prolonged QTc in the EEG recordings which were verified on their 12 lead ECGs. Two of them were newly diagnosed to have prolonged QTc as a result of this study.
Conclusion: QTc can be easily measured from lead I ECG (most commonly recorded) during EEG recordings. We recommend QTc measurement in standard EEG recordings to identify undiagnosed cardiac abnormalities and potentially prevent deaths.
4. Epileptia Partialis Continua in Progressive Myoclonic Ataxia and Coeliac Disease. A Mini Case Series. P. G. Sarrigiannis 1, J. Fotheringham1 and M. Hadjivassiliou2. (Dept of Clinical Neurophysiology1 and Neurology2, Royal Hallamshire Hospital, Sheffield, UK).
Coeliac disease (CD) is a recognised cause of progressive myoclonic ataxic syndrome. It is dominated by action and stimulus sensitive myoclonus of cortical origin with mild ataxia and infrequent seizures. Even though the basic movement phenotype in epileptia partialis continua (EPC) is usually focal myoclonus, to our knowledge this association with CD has not been previously reported. We describe 3 patients (2 male, 1 female), with progressive myoclonic ataxia syndrome and resistant coeliac disease. All 3 were affected by longstanding debilitating continuous (about 5Hz) irregular myoclonic twitches of variable intensity in the right side of their body (2 right upper limb and 1 face and tongue). Two of the patients had a history of secondarily generalised seizures that started and gradually spread from the chronically twitching regions. Electrophysiological examination with EEG - EMG polygraphy showed small duration EMG discharges (<50ms) with simultaneous activation of pairs of antagonists (where available) and a rostrocaudal recruitment order of the involved muscles, pointing towards a fast conducting corticospinal pathway. The technique of jerk locked back-averaging revealed time locked focal cortical transients in the contralateral fronto-central regions preceding the onset of the averaged EMG myoclonic jerks, by a few milliseconds (<40ms). We therefore conclude that all patients were affected by epileptia partialis continua.
5. Diagnostic Accuracy of Stimulation Single Fibre EMG Findings in Children with DOK7 Congenital Myasthenic Syndrome. J.C. McHugh, S.A. Robb, A.Y. Manzur, F. Muntoni and M.C. Pitt. (Department of Clinical Neurophysiology and Dubowitz Neuromuscular Centre, Institute of Child Health and Great Ormond Street Hospital, London. UK).
Background : DOK7 mutations account for a high proportion of congenital myasthenic syndromes (CMS) in childhood, but misdiagnosis is common. Early diagnosis is important as ephedrine or salbutamol treatment improves muscle strength and reduces morbidity.
Aim : To review the diagnostic accuracy of stimulation single fibre EMG (StimSFEMG) of orbicularis oculi in children with DOK7 CMS and identify any specific features which facilitate diagnosis.
Methods : Data from StimSFEMG of orbicularis oculi are presented from 11 children (4 female; age range 4 months to 12 years) with a genetically confirmed DOK7 CMS diagnosis. StimSFEMG data were recorded using concentric needle electrodes at a stimulus frequency of 10Hz, using a Keypoint electromyograph. Referral diagnosis was myopathy, myasthenia, or vocal cord paralysis. The number of fibres recorded by SFEMG in each child was 10-77 (median 33).
Results : All 11 children had abnormal jitter measurement as per automated analysis by the single fibre program: average mean consecutive difference (MCD) ≥26µs (normal ≤26µs) in 11/11 patients; more than 10% of individual fibres with MCD>34 in 10/11 cases; block being present in 3/11. However areas of normal muscle were frequently encountered, and extensive testing of the same muscle was required to ascertain abnormality in many cases.
Conclusion : StimSFEMG is a very useful aid in the diagnostic evaluation of children with suspected DOK7 CMS, abnormality was present in 100% of our series by conventional quantitative analysis. However, the patchy nature of abnormality on StimSFEMG is emphasised, and extensive study of muscle is indicated where DOK7 mutations are considered.
6. Comparison of the Multiple Sleep Latency Test and Epworth Sleepiness Scale in the Assessment of Neurological Sleep Disorders. A.St.J.E. Barker1, R.H. Kandler1 and G. J. Dennis2. (1Dept of Clinical Neurophysiology and 2 Dept of Neurology Royal Hallamshire Hospital, Sheffield, UK).
Background : The Epworth Sleepiness Scale (ESS) is a commonly used 8-question scale to assess sleepiness. Although validated in obstructive sleep apnoea its role in neurological sleep disorders is less well defined. ESS is cheap and easy to perform, whereas polysomnography (PSG) and multiple sleep latency testing (MSLT) are expensive and complex. We investigate whether ESS identifies patients with shortened multiple sleep latency (MSL) to optimise PSG/MSLT use.
Methods : ESS/MSLT results of 63 patients presenting to the Neurology Sleep Clinic with excessive daytime sleepiness were reviewed. Total ESS and individual question scores were compared between patients with and without objective evidence of sleepiness on MSLT.
Results : 18 patients were deemed Hypersomnolent with an MSL <8 minutes; 45 had normal MSL. ESS scores were abnormal (>11) in 52 and normal in 11 patients. There was no significant difference in total or individual ESS question scores between Normal MSL and Hypersomnolent groups (mean ESS 14 vs. 15). Compared to objective MSLT results, ESS sensitivity was 89%, specificity 20%, positive predictive value 31% and negative predictive value 82%.
Conclusion : A normal ESS suggests that MSLT may not be required. However an abnormal ESS is a poor predictor of true sleepiness. Research is needed to develop a better clinical questionnaire to help identify patients with neurological sleep disorders.
7. Cross Correlation of the Surface Electromyogram of Orbicularis Oculi, Masseter and Sternocleidomastoid. M. Lai¹, L. Williams², M. Baker¹,² and S. Baker². (Clinical Neurophysiology, Royal Victoria Infirmary¹ and Institute of Neuroscience, Newcastle University², Newcastle,UK).
This study examined whether a significant cross correlation(CC) of the surface electromyography(EMG) between the right and left orbicularis oculi(OOc),masseters and sternocleidomastoids is consistently found during a 1 minute sustained eye closure, jaw clench or neck flexion respectively and whether this is affected by the force of contraction.
In ten subjects, surface EMG was recorded from the pairs of OOc, massetters and SCM at 10, 20 and 50% of maximum voluntary contraction (MVC). The CC between the pairs of muscles was examined employing a blind separation method on the third order differentiated EMG signal.
In all subjects a consistent cross-correlogram was found between the OOc muscles at 50% MVC (r range 0.007-0.69,median 0.03). A cross-correlogram was frequently found in the massetter at 50% MVC (r range 0-0.045,median 0.006). The strength of the CC increased with level of effort. No convincing CC was found between the SCM’s at any level of effort, although an ill-defined CCg was seen in 2/10 subjects only at 50%MVC.
It may be appropriate to speculate whether these findings could be applied to the study of conditions with impaired corticobulbar projections.
8. Symptoms, Signs and a Proposal for Classification of Focal Ulnar Neuropathy Across The Elbow. A.A.A. Bajalan. (Hull Royal Infirmary, Hull, UK).
In 1958 William Feindel suggested a mechanism, akin to that of CTS, in the Cubital Tunnel as the cause of some cases of Tardy Ulnar nerve Palsy with or without history of fracture of elbow. In 1979, RG Miller coined the term of Cubital Tunnel Syndrome (CuTS) and used motor nerve conduction studies preoperative and intraoperatively to localise the site of the lesion between 1.5 cm and 3 cm distal to the medial epicondyle. Ever since, there has been an increasing trend to diagnose and treat patients with symptoms suggestive of ulnar neuropathy, with or without electrophysiological confirmation, as CuTS. I shall present the salient symptoms and signs of a cohort of 94 consecutive patients diagnosed with Focal Ulnar Neuropathy Across The Elbow (FUNE). Analysis of clinical and NCS characteristics of 76 of the cases, in whom the mode and course of onset of symptoms could be confidently ascertained, suggest that depending on mode of onset and progression of symptoms there is a case for classifying FUNE into Types I and II : Type I with sudden onset of maximum neurological deficit , and Type II with insidious onset and variable pattern of progression. Type I is more common than Type II, has a shorter history, has constant symptoms (not transient), tends to improve or stay stable, affects males and females equally, affects the left side is 5 times more commonly and shows more frequent electrophysiological evidence of conduction block across the elbow. Failure to distinguish the two types of neuropathy might be a major reason for the contradictory literature evidence regarding the efficacy and outcome of both conservative and surgical treatments.
BSCN abstracts 1 July 2011
Not peer reviewed