The role of early electroclinical assessment in improving the evaluation of patients with disorders of consciousness.

We all share the need to optimise the evaluation of patients with disorders of consciousness (DOC), given the high rate of misdiagnosis of vegetative state based on clinical examination. We believe that one way to do this is to optimise assessment from the early stages, in order to reduce discontinuity between the hospital and rehabilitation phases. While clinical observation remains the "gold standard" for the diagnostic assessment of patients with DOC, neurophysiological investigations (electroencephalography, short latency evoked potentials and event-related potentials) could help to further understanding of the pathophysiology underlying the state of unresponsiveness, differentiate coma from other apparently similar conditions (i.e., locked-in and locked-in-like syndromes), and potentially integrate prognostic evaluation with monitoring of the evolution of the clinical state. Moreover, these techniques have the considerable advantage of being available at the bedside. Discontinuity between the hospital and rehabilitation phases is rightly considered to be one of the critical points in the assessment of patients with DOC. In our view, a continuum of expert neurological assessment that begins with monitoring of the acute phase (focusing on evolution of primary brain damage and secondary complications) and follows through to the patient's discharge from the intensive care unit (focusing on the pathophysiology of brain damage and prognostication based on clinical, neuroimaging and neurophysiological tests) could help to: i) optimise the rehabilitation programme according to the expectations of recovery; ii) provide a basis for comparison with subsequent periodic re-evaluations; iii) ensure uniformity of assessment regardless of the heterogeneity of care facilities; and iv) characterise a subset of patients who, showing discrepancies between neurophysiological tests and clinical status, are more likely to undergo unexpected recovery.

Proposal of a new criterion for electrodiagnosis of meralgia paresthetica by evoked potentials.

We examined 19 subjects with meralgia paresthetica (bilateral in three cases), recording bilateral somatosensory-evoked potentials (SSEPs) after stimulation of the tibial posterior nerve (TPN) and cutaneous stimulation in the region of the lateral femoral cutaneous nerve (LFCN). We calculated the difference between TPN SSEPs and LFCN SSEPs cortical potentials, identifying a temporal parameter that we termed D(SEP). We defined D(SEP) normal values in a control group. D(SEP) evaluation showed good sensitivity and specificity (85.7% and 82.4%, respectively; accuracy, 83.3%) in discriminating affected limbs from unaffected. The main advantage of this method is to disengage from the necessity of contralateral comparison of LFCN recordings, joined with a reduction of interindividual variability of LFCN SSEPs amplitude and latency that often causes a lower sensitivity of other methods. As an interesting consideration, D(SEP) evaluation appears to mark out a possible subclinical involvement of LFCN in the asymptomatic side of patients with meralgia paresthetica.

Prediction of 'awakening' and outcome in prolonged acute coma from severe traumatic brain injury: evidence for validity of short latency SEPs.

OBJECTIVE: To evaluate the prognostic value of somatosensory evoked potentials (SEPs) in severe traumatic brain injury (TBI) considering both 'awakening' and disability. METHODS: SEPs were recorded in 60 severe TBI with duration of acute coma>7 days. N20-P25 amplitudes, their side-to-side asymmetry and CCT were measured. SEPs on each hemisphere were classified as normal (N), pathological (P) or absent (A). 'Awakening' and disability were assessed after at least 12 months using Glasgow Outcome Scale (GOS). SEP predictive value was compared with GCS and EEG reactivity RESULTS: Seventy-five percent regained consciousness. 29/60 had a good outcome (GOS 4-5) and 31/60 had a bad outcome (GOS 1-3). According to the ROC curve, SEP findings were classified in 3 grades. Grade I (NN, NP) had PPV of 93.1% for 'awakening' and 86.2% for good outcome. Grade III (AA) had PPV of 100% for bad outcome and 72.7% for 'awakening'. Grade II (PP, NA, PA) was associated with the wider range of outcome. A multivariate analysis including SEP grading, GCS and EEG reactivity did not increase the percentage of cases prognosticated by SEP alone. CONCLUSIONS: We confirm the high predictive value of SEPs in TBI, which is greater than GCS and EEG reactivity. Indeed, SEP grades I and III were able to predict the correct prognosis in more than 80% of severe TBI. Therefore, SEPs should be used more widely in the prognosis of severe TBI. SIGNIFICANCE: Differently from post-anoxic, in post-traumatic coma the presence of normal SEPs has a favourable predictive value both for 'awakening' and disability. We think that in literature enough attention has still not been paid to this finding.