Xanthochromia: yellow color is a red flag.

A 72-year-old previously healthy man consulted in our hospital for persistent moderate headache, accompanied by flexor pain of both thighs and low-grade fever for five days. Although the symptoms were worsened by motion, he noticed the flexor pain was most severe when taking a bow. On physical examination, he was fully alert and oriented to person, place, and time. His body temperature, blood pressure, pulse, and respiratory rate were 37.6 °C, 126/81 mmHg, 67 beats/min, and 16 breaths/min, respectively. His neck was supple. Kernig's and Brudzinski's signs were negative. There was a positive jolt accentuation test. No other neurologic findings were remarkable. Head computed tomography (CT) was normal; therefore, a lumbar puncture was performed, following suspicion of meningitis. Cerebrospinal fluid (CSF) analysis revealed 14 cells per microliter (mononucleosis was dominant), protein 185 mg/dL, and glucose 34 mg/dL. The opening pressure was 13 cmH2O. The CSF had an orange-yellow appearance (Figure 1a). This was suggestive of xanthochromia. Contrast-enhanced head CT and head magnetic resonance imaging were performed, and a ruptured anterior communicating artery aneurysm was detected (Figure 1 b). He was diagnosed with aneurysmal subarachnoid hemorrhage (SAH), which was classified as Grade 1 and Group 1, according to the World Federation of Neurological Surgeons subarachnoid hemorrhage grading scale and Fisher grade of cerebral vasospasm risk, respectively. Regarding the presenting symptoms, thigh flexor pain and low-grade fever were symptoms of breakdown of blood products within the CSF, which led to aseptic meningitis, also called meningismus. He was admitted to the intensive care unit for neurological and hemodynamic monitoring. Aneurysm repair with surgical clipping was performed, and after 4 weeks of rehabilitation, he was discharged ambulatory.