A 33-Year-Old Man with Progressive Diffuse and Focal Neuropsychiatric Signs without Localizing Correlates on Brain Imaging: A Systematic Approach to Diagnosis

INTRODUCTION: Novel expensive diagnostic tests are rapidly emerging. However, the answer to the most complex clinical presentations is often inferred from a systematic approach to the differential diagnosis. This is especially the case in neuropsychiatric disorders that present with a mix of neurologic and psychiatric symptoms. This case report fills a gap in the literature by providing a systematic differential diagnosis of such neuropsychiatric presentations associated with non-focal brain imaging. CASE PRESENTATION: A 33-year-old African-American man presented with confusion, weakness, and tremors. He initially noted memory problems and over the following six months progressively became confused, developed speech difficulties and left sided weakness and tremors. On exam, he was predominantly abulic but with intermittent and extreme mood lability. He lacked insight and his attention was poor. He had mild facial weakness and spastic hemiparesis with action tremors on the left side. Magnetic Resonance Imaging of the brain demonstrated non-specific diffuse parenchymal volume loss. His serum and cerebrospinal fluid studies were positive for Rapid Plasma Reagin and Veneral Disease Research Laboratory tests, respectively, suggesting a diagnosis of paretic neurosyphilis. CONCLUSION: This is a case of a young man with neurosyphilis who presented with progressive subacute cognitive decline, associated with focal neurological signs but no focal lesions on brain imaging. Neurosyphilis is often misdiagnosed on medicine, psychiatry, and neurology inpatient units. In this report, we present an approach to conceptualize similar cases and provide a differential diagnosis that will help reach an accurate diagnosis more efficiently. Further, it raises awareness regarding neurosyphilis, a devastating but easily treatable condition.