Behçet’s disease is a multisystem inflammatory disorder that can infrequently involve the nervous system. Central nervous system manifestations are classified as parenchymal or non-parenchymal, with the parenchymal form being more common. Parenchymal neuro-Behçet’s disease (NBD) predominantly affects the brainstem, particularly the midbrain and upper pons. We present a case of parenchymal NBD with an unusual cerebrospinal fluid (CSF) profile.

A 33-year-old woman with Behçet’s disease on infliximab infusions presented with one week of slurred speech, diplopia, and imbalance. Brain MRI demonstrated enhancement and concentric narrowing of the basilar artery with diffusion restriction in the pons. CSF analysis revealed pleocytosis (270 cells/µL, 85% lymphocytes), elevated protein (80 mg/dL), and markedly low glucose (25 mg/dL; serum glucose 104 mg/dL). Given concern for parenchymal NBD, she received intravenous methylprednisolone 1 g daily for five days. Due to the low CSF glucose and her immunosuppressed state, tuberculous meningitis was also considered.  CSF acid-fast bacillus culture was negative, and CSF adenosine deaminase levels were within normal limits. The disease course, absence of fever or meningeal signs, and degree of pleocytosis and protein elevation were consistent with an inflammatory etiology. The patient showed marked clinical improvement after high-dose steroid therapy and was discharged on an oral steroid taper with an increased infliximab dose.

In parenchymal NBD, CSF typically shows pleocytosis with elevated protein and normal glucose levels. Although some studies have reported mildly reduced CSF glucose in both acute and chronic NBD compared to non-NBD, values generally remain within normal limits, and markedly low CSF glucose is exceedingly rare. Tuberculous meningitis is a common mimicker of NBD with similar imaging features and should be carefully ruled out, particularly in immunosuppressed patients or those receiving anti-TNF therapy.