Retrosigmoid

Retrosigmoid refers to the retrosigmoid approach, a surgical corridor to the cerebellopontine angle (CPA) used in neurosurgery. The procedure creates access by removing bone behind the sigmoid sinus, either as a craniectomy or craniotomy, to reach the CPA while preserving midline structures. It is commonly employed for tumors, vascular lesions, or nerve decompression involving the CPA and adjacent brainstem.

Anatomy and overview of technique: the patient is positioned to optimize exposure of the posterior fossa, often in a lateral or park-bench position. A curved skin incision is made behind the ear, and a suboccipital craniectomy or craniotomy is performed posterior to the sigmoid sinus. The dura is opened with care to preserve the venous sinuses, and CSF drainage is used to relax the cerebellum before gentle retraction to expose the CPA and cranial nerves V through VIII. Microsurgical dissection and neurophysiological monitoring guide tumor removal or decompression while aiming to preserve function.

Indications and variants: the retrosigmoid approach is frequently used for vestibular schwannomas and other CPA tumors, meningiomas, epidermoids, and microvascular decompression for trigeminal neuralgia or hemifacial spasm. It can be performed as a craniectomy or craniotomy, with hearing preservation possible in select patients and tumor characteristics. In some cases, it serves as part of staged or combined strategies with other skull base approaches.

Risks and considerations: potential complications include injury to the sigmoid sinus or other venous structures, cerebellar contusion or edema, cranial nerve injury, CSF leaks, and postoperative imbalance in balance or hearing. The choice of retrosigmoid versus alternative approaches depends on tumor size, location, hearing status, and surgeon experience.