LAUSR

A non-smoking, left-handed, 75-year-old man was hospitalized because of subacute mental delirium and behavioral problems. Two and a half months before his hospitalization, he was found unconscious near his kitchen in the presence of a leaking 1-month natural-gas tank for a fuel-efficiency oven. He was admitted to the emergency unit with a carboxyhemoglobin (COHb) level of 3.1%, but did not require hospitalization. Several weeks later, he developed confusion, amnesic issues with unpredictable phases of aggressiveness, persecution mania and apathy (no hallucinations). Nocturnal alcohol consumption and hyperphagia were observed, but with no other symptoms of disinhibition. His neurological examination was normal. A brain computed tomography (CT) scan revealed frontotemporal lobe atrophy. Magnetic resonance imaging (MRI) using a fluid-attenuated inversion recovery (FLAIR) sequence showed hyperintense lesions involving both hippocampi, but predominantly on the left side, with no contrast enhancement (Fig. 1). Extensive blood tests, including a full blood count, electrolytes, liver and thyroid function tests, C-reactive protein (CRP), vitamin B12, folate, angiotensinconverting enzyme (ACE), and Borrelia and syphilis serological studies were all either negative or normal. Cerebrospinal fluid