A Teenager with an Anti-Glutamic Acid Positive, GQ1b Negative Miller Fisher Syndrome: An Atypical Presentation of Intracranial Hypertension with Incidental Chiari 1.5
Miller Fisher syndrome (MFS), considered a subtype of Guillain Barre Syndrome (GBS), is an acute, often postinfectious inflammatory demyelinating disorder usually presenting with a triad of ophthalmoplegia, ataxia, and areflexia. Intracranial hypertension (IH) rarely occurs with MFS, < 5% of cases, and few reported cases exist. We report a pediatric patient with a history of chronic tetracycline use presenting with severe headache, blurry vision, and diplopia with grade V papilledema that preceded the typical course of MFS; additional symptoms progressively included neck stiffness, multiple cranial nerve neuropathies, tinnitus, quadriparesis, dysmetria, gait ataxia, and areflexia. MRI imaging at presentation showed an incidental Chiari 1.5 malformation, bulging of the perioptic nerve sheath, flattening of the posterior sclera, and partially empty sella, consistent with IH. CSF studies showed albuminocytological dissociation with high CSF protein, serum negative GQ1b antibody, and positive GAD antibody. A 5-day course of IVIG, acetazolamide, and pulse dose steroids resulted in gradual improvement leading to full neurological recovery. Nerve conduction studies 3-4 weeks post-IVIG were consistent with MFS. We hypothesize that the combination of low CSF flow from the anatomical anomaly (Chiari 1.5) and chronic tetracycline use, with poor CSF arachnoid granulation reabsorption due to abnormal CSF protein levels may have precipitated the initial development of communicating hydrocephalus. The clinical improvement from pulse dose steroids and acetazolamide suggests that the pathophysiology was related to CSF flow and not exclusively driven by the antibody-mediated attack within myelin sheaths, as is typical of MFS. A major limitation of this case was the lack of opening pressure, CSF fluid analysis, and the absence of comprehensive CSF antibody studies given a low-volume tap due to safety concerns, including tonsillar herniation. More research is needed to further assess the pathophysiology relationship between Chiari 1.5 and different variants of acute demyelinating disorders, including MFS.
Keywords: Miller Fisher syndrome, intracranial hypertension, Chiari 1.5, anti-glutamic acid, decarboxylase antibodies
Citation: Rocha-Cabrero F, Shah A, Zamora M, Dudeck L. “A Teenager with an Anti-Glutamic Acid Positive, GQ1b Negative Miller Fisher Syndrome: An Atypical Presentation of Intracranial Hypertension with Incidental Chiari 1.5”. SVOA Neurology 2:6 (2021) Pages 191-194.
