Which part of the cerebellum is most sensitive to resection and should be avoided?

Cerebellar Vermis: The Most Sensitive Region to Avoid During Resection

The cerebellar vermis, particularly lobules VI-VII (declive, folium, and tuber), is the most sensitive region to resection and should be avoided whenever possible due to its critical role in postural balance, coordination, and eye movement control. 1, 2

Why the Vermis is Critical

Motor Control and Balance Functions

• The vermis receives dense projections from the primary motor cortex and motor areas on the medial wall of the cerebral hemisphere, making it a crucial integration site for cortical motor control 2
• Lobules VI-VII (declive, folium, tuber) are specifically critical for controlling postural balance, saccadic eye movements, and coordination including eye-hand coordination and bimanual coordination 1
• The vermis functions as part of the cortico-nuclear zone concerned with whole-body posture and locomotion 2
• Damage to vermis lobules VI-VII results in severe truncal ataxia, inability to maintain upright posture, and profound coordination deficits 1

Neuroanatomical Vulnerability

• The vermis serves as the site where cortical motor areas influence descending control systems for whole-body posture regulation 2
• This region is essential for anticipatory postural adjustments, and dysfunction can lead to dystonia 2
• The oculomotor vermis (lobules V, VI, VII) brings visual information critical for eye movement control 3

Clinical Implications for Surgical Planning

Approach Selection

• When operating in the posterior fossa, the suboccipital retrosigmoid approach requires cerebellar retraction but should minimize vermis manipulation 4
• For cerebellar infarctions with mass effect requiring decompression, suboccipital craniectomy with dural expansion should avoid vermis resection 4
• Lateral supracerebellar approaches are preferred over midline approaches when feasible to avoid vermis injury 4

Specific Surgical Considerations

• For pineal region tumors, choose surgical corridors that avoid vermis transgression—the lateral supracerebellar approach is suitable for most lesions extending laterally 4
• The midline infratentorial supracerebellar approach should only be used when the tumor is low-lying and the straight sinus angle permits access without significant vermis retraction 4
• Cerebellar hemisphere lesions should be approached laterally to completely avoid the vermis 4

Common Pitfalls to Avoid

• Never split the vermis for access to fourth ventricular or pineal region lesions when alternative approaches exist—the functional deficit from vermis injury often exceeds the risk of a more technically demanding lateral approach 1, 2
• Avoid excessive retraction of the vermis even when not directly resecting it, as retraction injury can produce similar deficits 4
• Do not underestimate the postoperative disability from vermis injury—patients may require prolonged rehabilitation and may never regain independent ambulation 1