Miller Fisher Syndrome

Miller Fisher syndrome (MFS) is an immune-mediated variant within the Guillain–Barré syndrome (GBS) spectrum. The bedside pattern is distinctive: ophthalmoplegia, ataxia, and areflexia. Ophthalmoplegia produces diplopia, impaired gaze, ptosis, or difficulty moving the eyes together. Ataxia in MFS is usually a sensory and vestibular problem rather than primary cerebellar destruction: inflammation affects proprioceptive fibres, so the patient has difficulty knowing where the limbs are in space and becomes markedly unsteady. Areflexia reflects disruption of the peripheral reflex arc. Anti-GQ1b IgG antibodies are directed against gangliosides concentrated in ocular motor nerves and proprioceptive pathways, which explains why eye movements, balance, and tendon reflexes are affected together. Symptoms often begin days to weeks after an infectious illness, but the antecedent illness may not be obvious. Limb strength can initially remain normal, which helps distinguish isolated MFS from the ascending weakness of classic GBS. That distinction is not a guarantee of safety. Some patients develop an MFS–GBS overlap pattern with limb weakness, bulbar dysfunction, autonomic instability, or respiratory muscle involvement. An experienced nurse notices function before a patient names the diagnosis. The patient...