Anisocoria without extraocular muscle impairment due to moderate traumatic brain injury with midbrain contusion: a case report

BACKGROUND: New-onset anisocoria is an important clinical clue to life-threatening intracranial injury. Anisocoria alone without impairment of extraocular muscles is a rare presentation of moderate traumatic brain injury (TBI). CASE PRESENTATION: A 79-year-old woman was transported to hospital soon after falling off a bicycle. Glasgow Coma Scale score on arrival was 11 (E3V3M5). On examination at admission, she was found to be drowsy. Bruising was seen around the right eye and pupil diameters differed (right, 4.5 mm; left, 3.0 mm; both reactive to light). Computed tomography of the head revealed hemorrhagic contusion in the left temporal lobe and left pretectal area of the midbrain, right clavicular fracture, and pulmonary contusion with fractures of the 3rd and 4th ribs. Magnetic resonance imaging confirmed hemorrhagic contusion of the midbrain. The patient achieved full recovery of motor and mental functions with conservative treatment and was discharged on hospital day 17. CONCLUSION: We encountered a case of anisocoria without major extraocular muscle impairment due to moderate TBI with midbrain contusion. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12883-023-03331-2.