Simon Boniface

Transient epileptic amnesia: a description of the clinical and neuropsychological features in 10 cases and a review of the literature

OBJECTIVES To clarify the clinical and neuropsychological aspects of transient epileptic amnesia (TEA) based on 10 personally studied cases as well as review of 21 previously published cases; and to propose tentative diagnostic criteria for the diagnosis of TEA. METHODS All 10 patients and informants underwent a standardised clinical interview. The radiological and neurophysiological (EEG) data were also reviewed in all cases. The diagnosis of transient epileptic amnesia was made on the basis of the following criteria: (1) there was a history of recurrent witnessed episodes of transient amnesia; (2) cognitive functions other than memory were judged to be intact during typical episodes by a reliable witness; (3) there was evidence for a diagnosis of epilepsy. This evidence was provided by either (a) wake or sleep EEG, or (b) the co-occurrence of other seizure types (if their roughly concurrent onset or close association with episodes of transient amnesia suggested a connection), or (c) a clear cut response to anticonvulsant therapy, or by a combination of these three factors. In addition all patients were administered a comprehensive neuropsychological test battery designed to assess verbal and non-verbal anterograde memory and retrograde memory for famous personalities and personal events. Their results were compared with those of 25 age and IQ matched normal controls. RESULTS TEA usually begins in later life, with a mean age of 65 years in this series. Episodes are typically brief, lasting less than one hour, and recurrent, with a mean frequency of three a year. Attacks on waking are characteristic. Repetitive questioning occurs commonly during attacks. The anterograde amnesia during episodes is, however, often incomplete so that patients may later be able to “remember not being able to remember”. The extent of the retrograde amnesia during attacks varies from days to years. Most patients experience other seizure types compatible with an origin in the temporal lobes, but transient amnesia is the only manifestation of epilepsy in about one third of patients. Epileptiform abnormalities arising from the temporal lobes are most often detected on interictal sleep EEG. Despite normal performance on tests of anterograde memory, many patients complain of persistent interictal disturbance of autobiographical memory, involving a significant but variable loss of recall for salient personal episodes. The epochs affected may predate the onset of epilepsy by many years. CONCLUSIONS TEA is an identifiable syndrome and comprises episodic transient amnesia with an epileptic basis, without impairment of other aspects of cognitive function. Future studies should consider the question of whether TEA reflects ictal activity or a postictal state, and the mechanism of the persistent autobiographical amnesia. It is hypothesised that the latter may result in part from impairment of very long term memory consolidation as a result of epileptic activity in mesial temporal structures.

Hyperventilation following head injury : Effect on ischemic burden and cerebral oxidative metabolism

Objective:To determine whether hyperventilation exacerbates cerebral ischemia and compromises oxygen metabolism (CMRO2) following closed head injury. Design:A prospective interventional study. Setting:A specialist neurocritical care unit. Patients:Ten healthy volunteers and 30 patients within 10 days of closed head injury. Interventions:Subjects underwent oxygen-15 positron emission tomography imaging of cerebral blood flow, cerebral blood volume, CMRO2, and oxygen extraction fraction. In patients, positron emission tomography studies, somatosensory evoked potentials, and jugular venous saturation (SjO2) measurements were obtained at Paco2 levels of 36 ± 3 and 29 ± 2 torr. Measurements and Main Results:We estimated the volume of ischemic brain and examined the efficiency of coupling between oxygen delivery and utilization using the sd of the oxygen extraction fraction distribution. We correlated CMRO2 to cerebral electrophysiology and examined the effects of hyperventilation on the amplitude of the cortical somatosensory evoked potential response. Patients showed higher ischemic brain volume than controls (17 ± 22 vs. 2 ± 3 mL; p ≤ .05), with worse matching of oxygen delivery to demand (p < .001). Hyperventilation consistently reduced cerebral blood flow (p < .001) and resulted in increases in oxygen extraction fraction and ischemic brain volume (17 ± 22 vs. 88 ± 66 mL; p < .0001), which were undetected by SjO2 monitoring. Mean CMRO2 was slightly increased following hyperventilation, but responses were extremely variable, with 28% of patients demonstrating a decrease in CMRO2 that exceeded 95% prediction intervals for zero change in one or more regions. CMRO2 correlated with cerebral electrophysiology, and cortical somatosensory evoked potential amplitudes were significantly increased by hyperventilation. Conclusions:The acute cerebral blood flow reduction and increase in CMRO2 secondary to hyperventilation represent physiologic challenges to the traumatized brain. These challenges exhaust physiologic reserves in a proportion of brain regions in many subjects and compromise oxidative metabolism. Such ischemia is underestimated by common bedside monitoring tools and may represent a significant mechanism of avoidable neuronal injury following head trauma.

Linear coupling between functional magnetic resonance imaging and evoked potential amplitude in human somatosensory cortex.

The interpretation of task-induced functional imaging of the brain is critically dependent on understanding the relationship between observed blood flow responses and the underlying neuronal changes. However, the exact nature of this neurovascular coupling relationship remains unknown. In particular, it is unclear whether blood oxygen level-dependent functional magnetic resonance imaging (BOLD fMRI) responses principally reflect neuronal synaptic activity. In order to address this issue directly in humans, we measured the increase in somatosensory evoked potential amplitude and fMRI BOLD changes to increases in intensity of median nerve electrical stimulation in five healthy non-anaesthetized subjects. We found that mean N20-P22 amplitudes increased significantly with stimulus intensity in all subjects, as did fMRI BOLD percentage signal intensity change. Moreover, the intensity of the BOLD signal was found to correlate linearly with evoked potential amplitude in four of the five subjects studied. This suggests that the BOLD response correlates with synchronized synaptic activity, which is the major energy consuming process of the cortex.

Multi-Modal Monitoring of Acute Brain Injury

OBJECTIVE To review the scientific basis for and utility of the traditional cerebral monitors used currently in neurointensive care, together with research techniques that are soon likely to become used in managing severe head injury and subarachnoid haemorrhage. DESIGN AND CONTENT Firstly, the pathophysiology of acute brain injury including cerebral haemodynamics, oxygen and metabolism and the role of secondary insults are discussed. Secondly, the importance of assessment of cerebrovascular autoregulation and reactivity is reviewed together with methods for its continuous non-invasive measurement using transcranial Doppler and intracranial pressure/arterial pressure recordings. Thirdly, the respective roles of jugular venous oxygen and brain tissue oxygen monitoring are analysed. Fourthly, the use of cerebral microdialysis is described, together with an overview of its utility. CONCLUSION Cerebral multimodal monitoring can be helpful for the optimal management of acute brain injury and essential for future exploratory trials of neuroprotective drugs.

Bilateral foot-drop in a patient with anorexia nervosa

We report the occurrence of bilateral foot-drop in a patient with anorexia nervosa. To the best of our knowledge this has not been reported previously. The underlying pathology was found to be peroneal nerve palsy probably related to mechanical pressure at the head of the fibula. Nutritional deficiency may also be implicated.

Monitoring emergence from coma following severe brain injury in an octogenarian using behavioural indicators, electrophysiological measures and metabolic studies: a demonstration of the potential for good recovery in older adults

This case study describes a multi-disciplinary investigation of the emergence from coma of an 80-year old female (KE) following severe traumatic brain injury. The relationship between cognitive/behavioural ability and the integrity of cerebral function was assessed using neuropsychological measures, positron emission tomography, electroencephalography, somatosensory evoked potentials and trans-cranial magnetic stimulation. These investigations were performed as KE was beginning to emerge from coma (4 weeks) and, again, ∼1 year following brain injury, when she was judged to have achieved her maximum level of recovery. Neuropsychological measures revealed improvement during the first year post-injury in KEs speed of information processing, memory and executive abilities. Electrophysiological and metabolic studies indicated a restoration of functional integrity that was consistent with the gradual recovery in higher brain function documented using behavioural procedures. This case study demonstrates the rehabilitation potential of pre-morbidly healthy older adults following severe traumatic brain injury.

Neurovascular relationships in human sensorimotor cortex can be modulated by movement

Introduction: The interpretation of fMRl is critically dependent on understanding the relationship between observed blood flow responses and the underlying neuronal changes. We have established a linear nemovascular coupling relationship between fMRl BOLD and somatosensory evoked potential (SEP) amplitude in human sensorimotor cortex using changes in stimulus intensity. Finger movement during a stimulus is known to attenuate electrical SEP responses in somatosensory cortex (movement gating), however it is also a common method of inducing fMRl BOLD activity in sensorimotor cortex, suggesting that electrical and haemodynamic cortical responses diverge. Here we examined the effects of finger movement during sensory stimulation on fMIU BOLD and SEP amplitude in sensorimotor cortex, in order to establish whether movement can modulate this relationship. Methods: Normal volunteers were subject to 0.2 millisecond square-wave electrical pulses delivered to the median nerve at the wrist, at 50 - 175 % of predetermined motor threshold. SEPs were recorded from contra-lateral parietal cortex, Cp3/4, referenced to Fz, over 450 averages. Gradient-echo EPI BOLD imaging was performed on a 3.0 Tesla Bruker Medical S300 using a blocked design with TB 4 sec. Imaging was acquired for all intensities, which were pseudo-randomised, then the experiment was repeated with subjects performing a self-paced thumb twitch during the stimulus. Images were analyzed using SPM99. Results: Without movement, fMBI BOLD responses paralleled changes in SEP N20-P27 amplitude (pcO.05) as both increased with increasing intensity (pcO.05; pcO.05 respectively). However, thumb movement increased fMRl BOLD signal intensity change (pcO.05) but caused a significant decrease in SEP N20-P27 amplitude across all intensities in all subjects (pcO.05). Conclusion: SEP amplitudes increased with increasing stimulus intensity, as did fMFU BOLD signal intensity changes, consistent with a close neurovascular coupling relationship. However the effect of simultaneous movement is to reset this relationship by increasing the cerebral blood flow response and suppressing the electrical response. The apparent coupling relationship can therefore be modulated by movement.

Electrocorticography: Current Trends and Future Perspectives

Electrocorticography: Current Trends and Future Perspectives . Edited by lf quesney, cd binnie, and g-e chatrian. (Pp172, US

EMGWaveforms: Video Companion to Electromyography and NeuromuscularDisorders.

161.00). Published by Elsevier Science, Amsterdam 1998. ISBN 0 444 82509 6. This is a book of 172 pages dedicated to the memory of Frank Morrell. It is a multiauthor text, originating largely from North America (with a notable United Kingdom contribution from the Maudsley Hospital). After a historical review including stimulation and recording techniques, novel approaches to using electrocorticography to predict surgical outcome after temporal lobe resection are presented convincingly and then followed by another chapter showing how parallel approaches can be applied in tailored …

Selective impairment of verb processing associated with pathological changes in Brodmann areas 44 and 45 in the motor neurone disease–dementia–aphasia syndrome

EMG Waveforms: Video Companion to Electromyography and Neuromuscular Disorders. Edited by david c preston andbarbara e shapiro. (Pp 56, £55.00). Published by Butterworth Heinemann, Oxford, 2000. ISBN 0750672293. This is a well constructed video with plenty of examples of EMG phenomena of interest to the trainee clinical neurophysiologist. Some common and unusual examples are included which provide an opportunity to recognise them, particularly …