Introduction: eight-and-a-half syndrome is an uncommon neurological disorder of the pontine tegmentum and the 7th cranial nerve, manifesting as conjugate horizontal gaze palsy (CHGP) and ipsilateral peripheral nerve paralysis (PFP). The main causes are cerebrovascular disease, demyelinating disorders, and infections. Neuropsychiatric systemic lupus erythematosus (SLE) as the etiology of internuclear ophthalmoplegia is exceedingly rare.

Case report A 38-year-old White female with a 22-year history of SLE presented with diplopia and left PFP. Four months previously, she started complaining of intermittent fever and headache, for which she sought medical care several times in another service, repeatedly being given the presumptive diagnosis of an acute viral illness. Upon admission in our hospital, physical examination was significant for CHGP, nystagmus, and gait ataxia. A rash on her upper trunk, suggestive of acute cutaneous lupus, was also noticeable. Laboratory results were remarkable for high titer anti-dsDNA (223 U/mL), low complement (C3 of 58 mg/dL, C4 of 9.7 mg/dL), and lymphopenia (250 cells/mm3). Cerebrospinal fluid (CSF) analysis revealed a mild pleocytosis (7 cells, 70% lymphocytes), protein of 80 mg/dL, and glucose of 43 mg/dL. Brain magnetic resonance imaging evidenced hyperintense lesions, on T2 and FLAIR sequences, on the white matter of the left centrum semiovale and the left facial colliculus, with mild enhancement on the pons, as well as foci of restricted diffusion on the left lateral ventricle and left basilar part of the pons, inferring microthrombi. Chest computed tomography exhibited mild bilateral pleural effusion. Transthoracic echocardiogram demonstrated mild pericardial effusion. Empirical treatment with acyclovir, ceftriaxone and ampicillin was started, covering the main possible etiologies of infectious rhombencephalitis. Culture for fungi and bacteria, real-time PCR assay for Listeria, and viral CSF panel all resulted negative, though, and the patient showed no improvement on antibiotics. Given the extensive evidence of multisystemic lupus activity, the patient was pulsed with methylprednisolone and cyclophosphamide, with satisfactory evolution.

Conclusion we presented an atypical case of cerebral vasculitis due to SLE presenting as eight-and-a-half syndrome.