Unilateral Abducens Nerve Palsy After Intracranial Pressure Normalization in Postpartum Cerebral Venous Sinus Thrombosis

Background : Cerebral venous sinus thrombosis (CVST) disproportionately affects women, with a reported incidence of approximately 7 per 100,000 deliveries in the peripartum period. Abducens nerve palsy in CVST is classically attributed to raised intracranial pressure (ICP) and typically presents as a bilateral false localizing sign. Isolated unilateral involvement emerging after ICP normalization is rarely reported. Case presentation: A previously healthy 22-year-old gravida 4, para 4 woman presented on postpartum day 11 with severe headache and left-sided paresthesia. MRI demonstrated diffusion restriction in the left frontal region, and magnetic resonance venography revealed extensive superior sagittal sinus thrombosis. Opening lumbar puncture pressure was 360 mmH₂O. She was started on therapeutic anticoagulation and acetazolamide. On postpartum day 17, despite documented ICP normalization to 210 mmH₂O and partial radiological recanalization, she developed new-onset left abducens nerve palsy with horizontal binocular diplopia. Examination confirmed isolated left lateral rectus weakness without papilledema or additional cranial nerve deficits. With continued anticoagulation, the palsy gradually resolved over eight weeks. Discussion : The emergence of unilateral abducens palsy after ICP normalization and during radiological recanalization argues against ongoing pressure-mediated traction as the sole mechanism. Alternative explanations include focal ischemic injury to the nerve, localized inflammation at Dorello's canal, or delayed reperfusion-related microvascular dysfunction. Conclusion : New focal neurological deficits emerging during the recovery phase of postpartum CVST warrant immediate reassessment, including repeat neuroimaging and ophthalmologic evaluation, even when ICP has normalized and radiological recanalization is underway.