[Traumatic primary brain stem injury and ambient cistern hematoma evaluated with magnetic resonance imaging]

Traumatic hemorrhage in the ambient cistern is thought to be an indirect indication of brain stem injury. In many cases such brain stem lesions cannot be clearly demonstrated by conventional CT scans. Magnetic resonance imaging (MRI) provides a more sophisticated display of the brain stem with improved contrast resolution of structures not appreciated on CT. We present four patients with traumatic ambient cistern hematoma on CT. They showed consciousness disturbance at the initial neurological examination and a Glasgow Coma Scale (GCS) of 7-10. All patients had hemothorax or clavicular fracture ipsilateral to the ambient cistern hematoma that suggested a severe mechanical force from the same direction. Axial, coronal and sagittal MRI scans were obtained with a super-conductive 1.5 T unit (Picker) within 6 days after trauma. Two standard pulse sequences were used; (1) Spin-echo (TR/TE = 500/20) or Inversion Recovery (TR/TI/TE = 3300/600/30) to obtain T1-weighted information and (2) Spin-echo (TR/TE = 2000/100) to obtain T2-weighted information. In case 1 (3-year-old girl) the hematoma which was thought to be located in the ambient cistern on CT was found to be present in the subpial region in the tegmentum on MRI. On T2 weighted image, a high signal intensity area was seen in the perifocal area. This area was demonstrated as a low density area on CT. This patient has remained in a persistent vegetative state 6 months after trauma. In case 3 (31-year-old man) CT demonstrated no abnormal findings in the brain stem. MRI demonstrated a high intensity area in the right cerebral peduncle and left tegmentum.(ABSTRACT TRUNCATED AT 250 WORDS)