Miniretrosigmoid approach

Mental Skills Required




Manual Skills Required




Mental Skills Required




Manual Skills Required




Basic information

  • Allows exploration of the entire cerebello-pontine angle (CP angle):
    • cranio-caudally – from the tentorium to the VII and VIII nerves
    • medial to lateral – from the middle cerebellar peduncule to lateral aspect of the cerebellar hemisphere
    • to the posterior petrous bone, internal auditory canal

To keep in mind

  • Consider whether the patient (location of the lesion are suitable for this type of approach)
  • Study carefully available images (CT, MR) to be prepared for anatomical rarities, use different section and projection 
  • Try to find the best route to the lesion with an avoidance of the excessive exposure and the retraction of brain tissue, otherwise use a different approach to reach the pathology
  • Keep in mind the general anatomy (skin layers, muscle, skull bones, transverse-sigmoid sinus junction, CP angle, cranial nerves, brainstem, cerebellum)
  • Be aware of possible slight distortion of the anatomy (patient is in the different position and the head is rotated – effect of the gravity)
  • Try to project the anatomy on the skin surface


Transverse-sigmoid junction, CP angle


Pathologies which are located in the CP angle.

Anatomy and important anatomical landmarks

  • Occipital artery
  • Skull bones – temporal bone, parietal bone, occipital bone, tip of the mastoid
  • Superior nuchal line (indicates the superior end of the skin incision)
  • Position of the sigmoid sinus – digastric groove (reference to the position of the sigmoid sinus, also indicates where to place the inferior limit of the skin incision)
  • Position of the transverse sinus – a line connecting the root of the zygoma and the inion
  • Asterion (can be palpated as a little depression, it is fundamental reference for placing the burr hole)
  • CP angle
  • Brainstem
  • Cranial nerves
  • Cerebellum, arteries (PICA, AICA, SCA)


  • Supine-lateral park bench position, 3/4 prone position or supine-lateral position
  • Put the Mayfield fixation with sparing of the skin incision location

Body positioning: supine lateral (45°), lateral (90°), lateral oblique (135°), semi-sitting

Head positioning: contralateral rotation 0° lateral tilt 5° flexion -10°

Red Flags

Avoid any site of compression by using multiple gel pads. Control the armpit and the position of the dependent arm (it should not be too stretched but neither too “pushed up”). The distance between the chin and the sternum should be at least 1 cm.


1. Skin incision N°22 scalpel blade

2. Dissection of muscular layers with monopolar cautery or scalpel

3. Burr hole with perforator

4. Preparation of the burr hole with dura separator

5. Craniotomy with high-speed drill

6. Bone drilling with high-speed drill

7. Dura incision with N°10 scalpel blade and scissor


SCA: Superior Cerebellar Artery

AICA: Anterior Inferior Cerebellar Artery

CN V: Cranial Nerve V, Trigeminal Nerve

CN VII: Cranial Nerve VII, Facial Nerve

CN VIII: Cranial Nerve VIII, Vestibulocochlear nerve

CN IX: Cranial Nerve IX, Glossopharyngeal Nerve

CN X: Cranial Nerve X, Vagus Nerve

CN XI: Cranial Nerve XI, Accessory Nerve

CN VI: Cranial Nerve VI, Abducens Nerve

SPV: Superior Petrosal Vein

SS: Sigmoid Sinus

TS: Transverse Sinus

MCP: Middle Cerebellar Peduncle

FLOC: Flocculus


1. Dura reconstruction

2. Bone fixation with microscrews

3. Muscle reconstruction

4. Subcutaneous/skin suture

Pterional Box: brain box for pteronial approach

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