The present study deals with observations on the "speech evoked potential"-a late positive potential evoked by word repetition. These potentials, evoked by "silent" repetition of polysyllabic words, were averaged and recorded from the scalp overlying the inferior frontal regions on both sides in 20 normal healthy subjects of ages ranging from 13-58 years. The potential had a triphasic negative, positive, negative morphology and was present over both hemispheres in left as well as right handed subjects. The main positive deflection and mean latencies of 219.2 msec and 221.6 msec and mean amplitude of 6.2 muv and 6.5 muv respectively on the left and right sides. Though there were interindividual variations in latency, amplitude and morphology, there was a high degree of intraindividual similarity and reproducibility in subjects. The variations in these parameters with age, sex and handedness are discussed. In 10 patients with cerebral lesions, the evoked potential was normal in 5 cases with right frontal lesions and showed abnormalities in 3 of 5 cases with left frontal lesions. The speech evoked potential may be useful in the further study of electrical correlates of speech output in speech disorders.
Tuberculous meningitis (TBM) causes significant morbidity and mortality. The primary objective was to re-examine the concept of "TB zone" and "ischaemic zone" in cerebral infarction in patients with tuberculous meningitis. The secondary objective was to evaluate cerebral infarction, vasculitis and vasospasm in tuberculous meningitis infections. Between 2009 and 2014, TBM patients were recruited. Neuroimaging was performed and findings of cerebral infarction, vasculitis and vasospasm were recorded. Infarcts were classified based on arterial supply and Hsieh's classification. Fifty-one TBM patients were recruited of whom 34 patients (67%) had cerebral infarction. Based on Hsieh's classification, 20 patients (59%) had infarcts in both "TB zone" and "ischaemic zones". 12 patients (35%) had infarcts in "ischaemic zone" and two (6%) patients had infarcts in "TB zone". In terms of vascular supply, almost all patients (35/36) had infarcts involving perforators and cortical branches. 25 patients (73%) and 14 patients (41%) had infarcts supplied by lateral lenticulostriate and medial lenticulostriate arteries respectively. 15 patients (37%) had vasculitis. Vasospasm was present in six patients (15%). 29 patients (85%) with cerebral infarction also had leptomeningeal enhancement (p = 0.002). In summary, infarcts involved mainly perforators and cortical branches, rather than "TB zone" versus "ischaemic zone".
A 38-year old female with underlying systemic lupus erythematosus was admitted with tuberculous meningoencephalitis. After an initial good response to anti-tuberculous treatment, she developed cerebral infarction and profound hyponatremia. This was due to cerebral salt wasting syndrome, which has only previously been described in 2 cases. The difficulties in diagnosis and management of this case are discussed.