SPET brain perfusion imaging in mild traumatic brain injury without loss of consciousness and normal computed tomography

We present SPET brain perfusion findings in 32 patients who suffered mild traumatic brain injury without loss of consciousness and normal computed tomography. None of the patients had previous traumatic brain injury, CVA, HIV, psychiatric disorders or a history of alcohol or drug abuse. Their ages ranged from 11 to 61 years (mean = 42). The study was performed in 20 patients (62) within 3 months of the date of injury and in 12 (38) patients more than 3 months post-injury. Nineteen patients (60) were involved in a motor vehicle accident, 10 patients (31) sustained a fall and three patients (9) received a blow to the head. The most common complaints were headaches in 26 patients (81), memory deficits in 15 (47), dizziness in 13 (41) and sleep disorders in eight (25). The studies were acquired approximately 2 h after an intravenous injection of 740 MBq (20.0 mCi) of 99Tcm-HMPAO. All images were acquired on a triple-headed gamma camera. The data were displayed on a 10-grade colour scale, with 2-pixel thickness (7.4 mm), and were reviewed blind to the patient's history of symptoms. The cerebellum was used as the reference site (100 maximum value). Any decrease in cerebral perfusion in the cortex or basal ganglia less than 70, or less than 50 in the medial temporal lobe, compared to the cerebellar reference was considered abnormal. The results show that 13 (41) had normal studies and 19 (59) were abnormal (13 studies performed within 3 months of the date of injury and six studies performed more than 3 months post-injury). Analysis of the abnormal studies revealed that 17 showed 48 focal lesions and two showed diffuse supratentorial hypoperfusion (one from each of the early and delayed imaging groups). The 12 abnormal studies performed early had 37 focal lesions and averaged 3.1 lesions per patient, whereas there was a reduction to an average of 2.2 lesions per patient in the five studies (total 11 lesions) performed more than 3 months post-injury. In the 17 abnormal studies with focal lesions, the following regions were involved in descending frequency: frontal lobes 58, basal ganglia and thalami 47, temporal lobes 26 and parietal lobes 16. We conclude that: (1) SPET brain perfusion imaging is valuable and sensitive for the evaluation of cerebral perfusion changes following mild traumatic brain injury; (2) these changes can occur without loss of consciousness; (3) SPET brain perfusion imaging is more sensitive than computed tomography in detecting brain lesions; and (4) the changes may explain a neurological component of the patient's symptoms in the absence of morphological abnormalities using other imaging modalities.