Identify the clinical features of One-and-a-half and Thirteen-and-a-half Syndromes. 

One-and-a-half Syndrome (OAHS) characterizes the presence of both an ipsilateral conjugate horizontal gaze palsy and an ipsilateral internuclear ophthalmoplegia. It serves as the primary clinical entity for a spectrum of exceedingly rare syndromes that feature unique combinations of neurological deficits with OAHS. Herein, we describe the first reported case of Thirteen-and-a-Half Syndrome in the setting of acute ischemic stroke.

A 51-year-old female with end stage renal disease, hypertension, and diabetes presented with complaints of binocular horizontal diplopia and severe headache. Initial exam revealed total rightward gaze paresis in both eyes and with leftward gaze, only the left eye could abduct where nystagmus was present, consistent with OAHS. She sequentially developed right lower motor neuron facial droop followed by right sided facial sensory loss on hospital days two and three respectfully. MRI Brain without contrast demonstrated the presence of acute ischemic stroke in the right dorsal pontine tegmentum.

Our patient illustrates the continuum One-and-a-half Syndrome Spectrum Disorders with onset of her facial droop denoting eight-and-a-half syndrome and facial sensory loss as thirteen-and-a-half syndrome. Collectively, they represent a constellation of symptoms exemplifying pontine neuroanatomy and clinical localization skills. Only three reports of thirteen-and-a-half exist on current literature review and occurred in the setting of CNS lymphoma, Neuromyelitis Optica, and brainstem cavernoma.

Acute ischemic stroke represents a novel etiology implicated in thirteen-and-a-half syndrome and highlights the expanding recognition of One-and-a-half Syndrome Spectrum Disorders in the fields of neuro-ophthalmology and vascular neurology.