Single photon emission tomography as a predictor of outcome in vegetative state of head injury.

Sir,

In a recent study, Nayak and Manepatra,[1] based on studies in 50 patients remaining in vegetative state (now referred to as “unresponsive wakefulness syndrome” (UWS)/2/),[2] stated that assessment of cerebral perfusion by single photon emission tomography (SPECT) is a better predictor of outcome than computerized tomography and/or magnetic resonance tomography. Already in 1972, SPECT measurement of total and regional cerebral blood flow (CBF) in patients with “apallic syndrome” following severe brain injury was shown to be an important tool for estimating the prognosis of these patients.[3] Correlation of CBF using SPECT and neuropathology in eight patients with vegetative state after brain injury revealed significant correlations between the decrease of CBF and the extent and pattern of brainstem damage, in particular with the degree of affection of the ascending activating reticular formation.[4] This association was later confirmed by positron emission tomography studies of CBF and glucose utilization in vegetative patients, involving, also, the cerebral cortex, basal nuclei and cerebellum.[5] However, there is still a need for prospective studies on the prognosis of the UWS in large, well-described cohorts of patients using standardized assessment and outcome scales.[2]