Evaluation and Management of Infratentorial Pathology
For suspected infratentorial pathology, immediately obtain non-contrast CT to assess for mass effect, hydrocephalus, and brainstem compression, followed by CTA to evaluate vascular occlusion if stroke is suspected, or MRI with DWI for ischemia detection when clinically stable.
Initial Imaging Strategy
CT Imaging First-Line
- Non-contrast CT is the most readily available and critical initial study for infratentorial pathology 1
- Rapidly identifies:
- Mass lesions requiring urgent surgical intervention
- Hydrocephalus with fourth ventricle obstruction
- Brainstem compression
- Obliteration of basal cisterns
- Hemorrhage location and volume
Advanced Imaging Based on Clinical Suspicion
For suspected posterior circulation stroke:
- CTA should be obtained urgently to identify basilar or vertebral artery occlusion 2
- CTA source images can calculate pc-ASPECTS (posterior circulation Alberta Stroke Program Early CT Score), which predicts outcomes
- CT perfusion adds diagnostic value with 74% sensitivity versus 31% for non-contrast CT alone in posterior circulation stroke 2
For suspected ischemia when clinically stable:
- MRI with DWI is the most sensitive test for posterior fossa ischemia 2
- However, DWI can be initially normal in 6-10% of cases (twice the rate of anterior circulation) 2
- MRI prior to intervention independently predicts good outcomes in basilar occlusion 2
- pc-ASPECTS ≥8 on DWI is the only independent predictor of favorable outcome (OR 3.9) 2
Critical Management Decisions
Cerebellar Hemorrhage
Surgical evacuation is indicated for:
- Hematoma >3 cm or >15 mL
- Deteriorating clinical examination
- Impending brainstem compression
- Clinical hydrocephalus with fourth ventricle obstruction
- Radiographic obliteration of basal cisterns 1
The perceived life-saving benefit of surgery for cerebellar ICH precludes equipoise for randomized trials 1, making this a standard-of-care intervention despite limited high-quality evidence.
Posterior Circulation Stroke
For basilar artery occlusion:
- Mechanical thrombectomy is the standard intervention
- CTA vascular collateral score and patency of distal basilar artery correlate with good outcomes (mRS ≤3) 2
- Cerebral blood volume pc-ASPECTS ≥8 significantly reduces mortality risk (RR 3.8) 2
Intracranial Pressure Management
For elevated ICP from infratentorial pathology:
- Consider simultaneous supra- and infratentorial ICP monitoring as pressure gradients exist between compartments 3
- Intraparenchymal cerebellar monitoring may be more sensitive for focal swelling and ischemia 3
- Standard ICP management includes:
- Head elevation
- Adequate sedation and analgesia
- Hyperosmolar therapy (mannitol or hypertonic saline)
- CSF drainage when appropriate
- Hyperventilation only for life-threatening ICP elevation 4
Key Clinical Pitfalls
Cerebellar syndrome manifestations:
- Occurs in 65.6% of infratentorial tumors versus 31.5% of supratentorial (OR 3.2) 5
- Nystagmus is significantly more common with infratentorial lesions 5
- Do not delay imaging based on absence of cerebellar signs—they may be subtle or absent early
Posterior circulation stroke diagnosis:
- DWI can be falsely negative early—repeat imaging if clinical suspicion remains high 2
- Non-contrast CT has only 31% sensitivity for posterior circulation ischemia 2
- CTP significantly improves detection with 74% sensitivity and 80% negative predictive value 2
Timing considerations:
- Infratentorial pathology can deteriorate rapidly due to limited space and proximity to vital brainstem structures
- Surgical intervention for cerebellar ICH should not be delayed when meeting criteria above 1
- For basilar occlusion, extent of brainstem ischemia on CTA source images relates to mortality 2