1. Prolonged QTc Interval May Not be Detected in Most Epileptic Subjects. Ng K¹., Youl B¹., Turner S²., Schapira A¹. (¹Dept of Clinical Neurosciences, Royal Free Hospital Hampstead NHS Trust and Department of Cardiology, ²Kings College Hospital NHS Trust, London, UK).

Prolonged QT interval is one possible mechanism for sudden unexplained death in epilepsy (SUDEP). Many studies have highlighted the relationship between recurrent focal or generalised brain activation and myocardial injury which may predispose to a terminal dysrhythmia in the setting of an acute seizure. This study analysed 2-lead ECG determined QT intervals from EEG examinations in 38 subjects deemed to have epilepsy by clinical or EEG criteria, compared to 78 non-epileptic subjects referred for EEG. There was no QTc prolongation in the epileptic subjects compared to the subjects without a diagnosis of epilepsy (mean QTc interval 405.5 vs 412.4ms). Univariate analysis of widely-held risk factors for SUDEP showed a non-significant tendency for patients with generalised seizures and potentially limbic activation to have higher values. Previous studies of QT interval have demonstrated small but significant prolongations in subjects at risk of SUDEP, a different population from our study. We chose to see if such a difference existed in the epileptic population as a whole which appears not to be the case.

2. The Continuum of PLEDs, Periodic Complexes and Generalised Epileptiform Discharges: Observations and Hypotheses. Kalamangalam G. (Departments of Neurology, Southern General Hospital, Glasgow, UK and The Cleveland Clinic Foundation, Cleveland, OH, USA).

Structural brain correlates of periodic lateralised epileptiform discharges (PLEDs) are commonly believed to be large, acute, cortical processes. Recent neuroimaging studies (Ref) however demonstrate that structural lesions are not mandatory in PLEDs, and when present, may be subcortical and/or chronic. Other, electroencephalographic, studies of ‘cortical’ and ‘subcortical’ PLEDs have demonstrated statistically significant population differences.

These results lead to the consideration of mechanisms for large-scale oscillatory synchrony in the cerebral cortex and subcortex. The experimental literature suggests that such synchrony may be abstracted as ‘thalamocentric’ or ‘corticocentric’. This partition is seen to be a conceptually compelling way of viewing EEG periodic complexes (PCs) as well as generalised interictal epileptiform discharges (GIEDs). PLEDs differing in their structural brain correlates (as above) may be consistently classified within such a scheme. It is argued, therefore, that PLEDs, PCs and GIEDs are specific entities in the continuum of a common framework for large-scale rhythmogenesis in the brain.

Ref: Gurer, et. al., 2004 Clin. EEG Neurosci. 35 (ii) 88-93

3. The EEG in Sporadic Creutzfeldt-Jakob Disease. Cooper S.A., Will R. G., Knight R. S. G. (The National CJD Surveillance Unit, Edinburgh, UK).

The EEG is useful when diagnosing sporadic CJD (sCJD). Periodic sharp wave complexes have been reported with a sensitivity of 66%. The association of certain “atypical” clinical features with EEG sensitivity is unknown.

Aim: Using standardised criteria to review EEGs in sCJD. To correlate certain clinical features with EEG results.

Method: A review of pathologically-proven sCJD EEG results reported by the National CJD Surveillance Unit over a 12 year period. Those with an age at onset <50yrs, disease duration >2 yrs, a pure visual or cerebellar syndrome at onset were identified (“atypical” cases) and compared with a “core group” (n=133) lacking these features.

Results and conclusions: 416/485 pathologically proven sCJD cases had an EEG and 162 (39%) were typical. The young, long duration cases and pure cerebellar onset cases were less likely to exhibit a typical EEG (p=0.018, p=<0.001 and p=0.025 respectively) than those in the “core group”. A typical EEG was associated with shorter disease duration amongst clinically “atypical” cases and being bed-bound with myoclonus. A typical EEG was associated with methionine homozygosity at PRNP gene codon 129. EEG sensitivity is lower in our cohort and this may relate to failure in repeating recordings as the disease progresses.

4. The Utility of Inducing Non-Epileptic Seizures during Outpatient Short Video EEG (SVEEG). Russell A.J.C., Mallik A., Oto M., McGonigal A., Duncan R. (Dept. of Clinical Neurophysiology and West of Scotland Regional Epilepsy Service, Southern General Hospital, Glasgow, UK).

Over the last 5 years, 449 patients with suspected psychogenic non-epileptic seizures (PNES) have undergone a SVEEG using the suggestion techniques outlined previously in a randomised study.

231 (51%) had events, 223 of these were non-epileptic, and 180 were habitual psychogenic non-epileptic seizures (PNES). 11/180 patients with habitual PNES have undergone further EEG studies, changing the diagnosis in two to ‘epilepsy and PNES’.

230 tests were ‘non-diagnostic’. 66 have undergone further EEG monitoring with a definitive diagnosis reached in a further 38.

Interictal EEG has shown epileptiform abnormalities (EA) in 41/449 patients (9%). 16 patients with interictal EA, including eight who had an epileptic event during the SVEEG, have a diagnosis of epilepsy only. 7 have both epileptic and PNES. 119/449 (26%) had non-epileptiform EEG abnormalities which may have contributed to earlier diagnostic uncertainty.

This technique remains a useful test to confirm PNES without the need for long term monitoring. Interictal EEG when unequivocally abnormal predicts concurrent or past epilepsy and may guide AED withdrawal.

5. The Somatosensory N35:P25 Amplitude Ratio: a New Investigative Tool for Dystonia? Ng K, Jones SJ. (The National Hospital for Neurology and Neurosurgery, Queen Square, London, UK)

600 consecutive patient median nerve SEPs were retrospectively analysed to study the clinical associations of a feature where cortical N35 amplitude exceeded that of the preceding P25 (C3’/4’-Fz).Compared with 27 healthy controls, this feature was more common in patients (23.1% vs 7.4%;95%CI 5.3%-26.2%;p=0.003). Dystonia was more often present in patients with (9.5%) than without (1.5%) the feature (95%CI 2.9%-12.8%;p=0.002), as was myoclonus with (16.5%) than without (6.5%) the feature (95%CI 3.5%-16.6%;p=0.003). The sensitivity was 65% and specificity 78% for dystonia. These relationships held true when 72 patients with and 72 without the feature, showing no other SEP abnormality were compared assessing diagnosis, symptomatology and signs. Its presence was negatively associated with suspected or definite central demyelination, and sensory symptoms (p<= 0.005). Further comparison of N35:P25 ratios in the movement-disordered subjects without sensory involvement with controls strengthened the association with dystonia (R median 0.86vs 0.54, L median 0.82vs 0.59; p=0.003-4). This novel finding in an established test may prove useful in the clinical evaluation of a condition where there is increasing evidence of disordered sensorimotor integration.

6. Electrophysiological Findings in Distal Acquired Demyelinating Symmetrical (DADS) Neuropathy – Report of 3 cases. Ponnusamy A¹, Arunachalam R², Chandrasekera CP¹ and Mills KR². ⁽¹Hurstwood Park Neurological Centre, Haywards Heath, UK and ²King’s College Hospital, London, UK).

DADS neuropathy is a subgroup of acquired, symmetrical, chronic demyelinating polyneuropathy with predominant sensory involvement and minimal weakness limited to distal muscles. Nerve conduction studies (NCS) show symmetrical generalised motor slowing with absent sensory potentials (SAPs). Distal motor latencies (DMLs) are disproportionately prolonged. We report electrophysiological findings in 3 cases of DADS neuropathy.

All patients were males over 70 years who presented with slowly progressing chronic sensorimotor polyneuropathy. NCS showed severe demyelinating features. SAPs were absent; there was generalised motor slowing with dispersion. The DMLs were very prolonged and the Terminal Latency Indices (TLIs) were reduced. The TLI in the ulnar nerve in the 3 patients were 0.13, 0.22 and 0.09 (Normal 0.48±0.06). IgM paraprotein (Kappa) was present in 2 patients. These two had no response to immunotherapy. The patient who had no IgM paraprotein had spontaneous partial resolution of symptoms, with the ulnar TLI improving from 0.09 to 0.23. DADS neuropathy can be further sub-classified depending on the presence or absence of a circulating paraprotein (DADS-M and DADS-I neuropathy respectively). 50%-70% of patients with DADS-M type have anti MAG antibodies, but show poor response to immunotherapy. The response in DADS-I is intermediate between DADS-M and CIDP.

7. A Study of 24 Patients with Intermittent Sensory Symptoms in the Hands. Smith I.S¹. and Hasan S.S². (The General Infirmary at Leeds¹ and York Hospital², Yorkshire, UK).

The differential diagnosis of carpal tunnel syndrome and ulnar neuropathy is usually easy but in a small proportion of patients, it can be difficult.

Twenty four such patients were studied. They all had intermittent sensory symptoms which predominantly but not exclusively involved the ulnar territory of the hand. An unexpected finding was that the distribution of the symptoms varied. Sometimes, the symptoms were consistent with one or more of the accepted variants of carpal tunnel syndromes eg. The thumb, index and middle finger or all five digits. At other times they were confined to the ulnar territory. Another common pattern was symptoms in the middle, ring and little fingers. Each patient had a different combination of symptoms, with up to 5 different patterns seen in an individual. No patient had any neurological signs in the upper limbs.

Nerve conduction studies were carried out and the results compared with a group of sex, age and occupation matched controls. There were significant differences between the two groups in both median and ulnar conduction, consistent with the presence of mild or moderate median and mild ulnar neuropathies in the patients, although the level of ulnar involvement (wrist or elbow) was uncertain.

We propose that these patients have a combination of carpal tunnel syndrome and mild ulnar neuropathy, although the cause of the symptoms affecting the middle, ring and little fingers is uncertain.

8. Is the Use of a Disposable Concentric Needle Electrode for Jitter Measurements Justifiable? A Validation Study in Myasthenia Gravis. Sarrigiannis P.G., Kennett, R.P., Farrugia, M.E. and Read S. (Radcliffe Infirmary, Oxford, UK).

As prion proteins are present in muscles of patients with spongiform encephalopathy, there is a theoretical risk of transmitting prion disease with reused needle electrodes. Because of this, we have employed disposable concentric needle electrodes (CNE) for measurement of neuromuscular jitter since 1999. This study established the efficiency of the modified technique in patients with myasthenia gravis (MG) using receiver-operator characteristic (ROC) curves. These were constructed using jitter values from 20 healthy subjects and 56 myasthenic patients. The disease group was selcted from consecutive patients based on the ‘gold standard’ of a positive acetylcholine receptor (AChR) antibody titre and a clinical diagnosis made independently by an expert in neuromuscular diseases. Recordings were made using a Medelec Synergy electromyography, a disposable ‘facial’ CNE (leading off area of 0.28mm²), and low frequency filtering set at 2KHz. Two ROC curves were drawn, one using mean MCD values from orbicularis oculi and extensor digitorum communis, and other using a value that defined 10% of potential in the sample as being abnormal. The sensitivity obtained from the MCS curve was 92.9% (95% confidence interval 82.7-98%), and the ‘outlier’ curve of 96.4% (95% Cl 87.5%-99.6%) both with no false positives. From these results we defined the upper limit of normal for MCD, which is similar to that published for the standard SF EMG electrode. We conclude that a disposable CNE is a valid alternative to the traditional SF EMG electrode in the assessment of patients with myasthenia gravis.

9. Disruption of Sequential Finger Movements by Transcranial Magnetic Stimulation. Arunachalam R., Weerasinghe V.S. and Mills K.R. (Academic Unit of Clinical Neurophysiology, King’s College Hospital, London, UK).

Fine dextrous movement of the fingers is often the first to be lost and the last to recover in pyramidal lesions. To investigate the complex system of rapid independent finger movement we developed a simple model: the rapid sequential tapping of middle and index fingers. We observed striking differences in the ability to perform sequential taps depending on the direction of tapping, with middle index (M®I) taps considerably faster than index middle (I®M) taps. By analysing the EMG bursts associated with these taps we have shown that the differences reflect the cortical control of finger movement rather than a peripheral biomechanical effect. With ethics committee approval, transcranial magnetic stimulation was applied at the time of the first tap and its effect on the subsequent tap studied in 7 healthy subjects. Stimulus intensity was varied from 1.0 to 1.4 times the threshold intensity. The second tap failed to emerge in both directions of tapping. With higher intensities (1.3 and 1.4 times threshold), however, the failure rate was significantly higher for I®M taps (p<0.02). This further supports the notion that the cortical control of finger tapping is dependent on finger order. Motor control of finger movement may be hard-wired in the faster (M®I) direction to facilitate grasping.