[Two cases of isolated ambient cistern hematoma after head injury].

This is a report of two cases of isolated ambient cistern hematoma after head injury. Isolated small hematomas in the ambient cistern after head injury are considered indirect evidence of brain stem injury. In such cases the initial neurological signs are often severe, but the ultimate prognosis is almost always good or excellent. Our patients showed hardly any neurological signs, and their head trauma was not very severe. Isolated ambient hematomas are the result of injury to small vessels or of mild contusions of the brain stem produced by the edge of the tentorium. In case 2, MRI revealed small, high signal intensity near the hematoma, and this sign was interpreted as evidence of mild brain stem injury. We think our patients had very mild brain injuries which were unaccompanied by diffuse axonal injury.