26 Retrosigmoid Approach The retrosigmoid approach is a lateral approach to the posterior fossa compartment. It is suitable for surgical exposure of the ipsilateral surface of the cerebellar hemisphere, the posterior surface of the petrous bone, as well as the cisternal space defined as cerebellopontine angle (CPA). Surgical exposure can be further widened caudally toward the magnum foramen and rostrally until the tentorium, which can be cut and opened, providing a transtentorial route to reach the supratentorial space. The approach is extremely versatile and can be tailored according to the pathology, which must be treated. The approach is indicated for lesions involving the CPA as well as for microvascular decompression in case of trigeminal neuralgia. • Neoplastic and vascular disorders of the cerebello-pontine angle (CPA). • Neurovascular decompressions in trigeminal neuralgia. • Somatosensory evoked potentials. • Facial nerve electromyography. • Auditory-brain-stem-response. • Position: Patient is positioned in lateral decubitus; the contralateral arm is positioned below the surgical table with a slight flexion. • Head: The head is positioned neutral, parallel to the ground, fixed on a Mayfield head holder. • The ipsilateral shoulder is slightly displaced inferiorly, with cushions under contralateral armpit and between the knees. • The ipsilateral thigh is flexed and prepared for possible fat and fascia harvest. • Linear incision ◦ Landmark: Mastoid tip. ◦ Starting point: Incision starts 2 cm behind the external ear at the level of the pinna. ◦ Course: Incision line runs inferiorly in a straight line. ◦ Ending point: It ends 1 cm inferior to the mastoid tip. • Muscles ◦ Incised according to the skin incision. ◦ Subperiosteal dissection is carried out laterally, medially, superiorly and inferiorly. • Mastoid emissary vein. • Vertebral artery at the atlanto-occipital joint. • Burr holes (Fig. 26.3) ◦ I: The burr hole is placed on the asterion and performed with a regular cranial perforator or a high-speed drill. • Craniotomy landmarks (Fig. 26.4) ◦ Posteriorly: Craniotomy runs about 3 cm posterior to the burr hole. ◦ Inferiorly: It runs 4 cm inferiorly, turning anteriorly, just parallel to the burr hole.
26.1 Introduction
26.2 Indications
26.3 Neurophysiological Monitoring
26.4 Patient Positioning (Fig. 26.1)
26.5 Skin Incision (Fig. 26.1)
26.6 Soft Tissue Dissection (Fig. 26.2)
26.6.1 Critical Structures
26.7 Craniotomy
Neupsy Key
Fastest Neupsy Insight Engine
