Headache due to spinothalamic tract injury in patients with mild traumatic brain injury: Two case reports.

Headache is the most common physical complaint reported by the following traumatic brain injury (TBI). Several studies using diffusion tensor tractography (DTT) have demonstrated that injury of the spinothalamic tract (STT) is a pathogenetic mechanism of central pain following TBI. However, no study of headache due to injury of the STT has been reported. Patient 1 was a 52-year-old female who suffered head trauma resulting from an in-car traffic crash. While sitting in a passenger seat in a moving vehicle, another vehicle suddenly hit the car from the right side. Her head hit the door and she suffered a flexion-hyperextension-rotation injury. She began to feel headaches in both fronto-parieto-occipital areas approximately 2 weeks after the crash. The characteristics and severity of pain were as follows: constant tingling and intermittent stabbing pain without allodynia or hyperalgesia (visual analogue scale score: 7). Patient 2 was a 50-year-old male who suffered head trauma from a flexion-hyperextension injury that occurred after being hit from behind by a vehicle while driving his car. He began to feel headache in both fronto-parieto-occipital areas the day after the crash: constant tingling pain without allodynia or hyperalgesia (visual analogue scale score: 6). The patient 1 was diagnosed as mild TBI due to head flexion-hyperextension-rotation injury. The patient 2 was diagnosed as mild TBI due to head flexion-hyperextension injury. Clinical assessment and DTT were performed at 5 months (patient 1) and 10 months (patient 2) after the initial injury. On DTTs of patient 1 and 2, the STTs showed narrowing in both hemispheres. In addition, discontinuations at the subcortical white matter were observed in both hemispheres in patient 2. Headache due to injury of the STT was diagnosed in patients with mild TBI. Precise diagnosis of central pain from other types of pain is clinically important because the management of central pain is quite different from those for other types of pain. Our results suggest that headache might be ascribed to the injury of the STT in patients with mild TBI. Therefore, we recommend evaluation of the STT using DTT in patients with mild TBI who complain of headache having the characteristics of neuropathic pain.