Written by Dr William Maish
Cranial nerve VI palsies are typically well-mapped, and most clinicians rely on the classical neuroanatomical model when localising lesions in the dorsal pons. Yet occasionally a clinical presentation forces a reassessment of assumptions we take for granted. This case report examined an unexpected pattern of abducens fascicular involvement following recurrent haemorrhage from a pontomedullary cavernous malformation.
The patient’s pattern of deficits—isolated abducens fascicular palsy with preserved expected nuclear findings—did not align neatly with established projections of the abducens nucleus. Through detailed imaging review and comparative primate neuroanatomy, we proposed a plausible anatomical variant involving dorsomedial splaying of projection fibres around the nucleus.
While neuroanatomical variants are uncommon, this case demonstrates why clinical neuroanatomy must remain dynamic. Deviations from textbook patterns matter: they change how we interpret MRI findings, refine our surgical approaches and deepen our understanding of the relationship between developmental venous anomalies, cavernous malformations and focal neurological deficits.
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Written by Dr William Maish
MD MBA MPH FHEA JD (in prog.)
Found of Medly & Medly Health
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