Acute-Onset Bilateral External and Internal Ophthalmoplegia: A Rare Presentation of Miller Fisher Syndrome in a Pediatric Patient.

Miller Fisher syndrome (MFS) is a rare Guillain-Barré syndrome (GBS) variant. The global incidence of GBS is approximately one to two in 100,000 children (aged 0 to 15 years) per year. Miller Fisher syndrome represents a further small subset, with the incidence being one to two in 1,000,000 children. It affects all age groups; however, adult males are more commonly affected, with a male-to-female ratio of 2:1. It usually presents with a triad of ataxia, areflexia, and ophthalmoplegia. The hallmark sign of MFS is ophthalmoplegia, with internal ophthalmoplegia being more common. Pupillary response may vary from sluggishly reactive to non-reactive. The external ophthalmoplegia observed in MFS is bilateral and symmetrical, but some unilateral cases have also been reported. Internal and external ophthalmoplegia occurring together in a pediatric patient has not been reported in the literature to the best of our knowledge. Thus, we are reporting this case to highlight the rare presentation of internal and external ophthalmoplegia in a pediatric patient. Here, we present a case of a 10-year-old male child who presented with sudden onset ataxia, headache, blurring of vision, diplopia, and four-quadrant eye movement restriction. On examination, the child was overweight and had external and internal ophthalmoplegia (third, fourth, and sixth cranial nerve involvement) with ataxia and hypertension. There were no motor deficits or any other cranial nerve involvement. The GBS variant was considered the initial diagnosis. There was no history of previous infection. We investigated the case, and a lumbar puncture was done. Cerebrospinal fluid (CSF) analysis was normal, and anti-GQ1b antibodies were present. The patient was started on steroids and intravenous immunoglobulin (IVIG) and recovered slowly.  Most patients of MFS experience complete recovery within several weeks to months. Anti-GQ1b antibody positivity holds very crucial diagnostic value for MFS. IVIG and steroids are the treatments of choice for moderate to severe cases. This case report emphasizes the importance of suspecting and diagnosing MFS, particularly in pediatric patients and considering it as a differential diagnosis for acute-onset internal and external ophthalmoplegia with ataxia.