A patient is admitted to a psychiatric hospital after having been picked up by the police for making inappropriate sexual advances. A detailed psychiatric interview demonstrates deficits in memory, insight, judgement, personal appearance, and social behavior. The patient is witnessed experiencing a possible epileptic seizure. Over a period of several years, motor findings also develop, including relaxed, but expressionless facies, tremor, dysahria, and pupillary abnormalities. Which of the following tests performed on his cerebrospinal fluid would most likely be diagnostic?

The patient has neurosyphilis, specifically general paresis, a term that means "general paralysis of the insane." In this late sequela of syphilitic infection which occurs 5 to 20 years after infection, patients develop mental deterioration, which precedes motor system deterioration, leading eventually to "general paralysis" with mutism and incontinence. The abnormalities may be conveniently recalled using paresis as a mnemonic for personality, affect, hyperactive reflexes, Argyll Robeson pupils in the eyes, defects in the sensorium, intellectual decline and deficient speech. Specific anti-treponemal tests such as FTA-ABS are usually positive on both serum and cerebrospinal fluid. The cerebrospinal (CSF) glucose in neurosyphilis is usually normal. Gram's stain of CSF will not demonstrate spirochetes in neurosyphilis. The CSF lymphocyte count is typically elevated in neurosyphilis, but this is a non-specific finding.