Spontaneous Cerebellar Hemorrhage

Several factors must be considered before deciding to operate:

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  Size of hematoma: Surgical intervention generally is indicated for lesions of greater than 3 to 4 cm to improve clinical condition and prevent secondary deterioration due to cerebellar swelling and herniation. ^{9 , 11}

  
  
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  Neurologic status: The presence of signs and symptoms attributable to hydrocephalus (agitation, confusion, lethargy), brainstem compression (sixth or seventh nerve palsy, horizontal gaze paresis, hemiparesis), or coma should prompt emergent surgical intervention.

  
  
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  Time since ictus: Patients presenting within 6 to 48 hours of hemorrhage often experience neurologic deterioration due to a combination of swelling and re-hemorrhage. By contrast, those presenting 5 to 7 days after the initial bleed typically improve or remain stable.

  
  
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  Issues tangential to the primary pathology: Age, comorbidities, social situation, and advance directives also must be taken into account. A nursing home–confined, 80-year-old patient with dementia and multiple medical comorbidities, presenting in coma, may not an appropriate candidate for surgical management. ^{11 – 14}

Cerebellar Infarction

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  The indications for decompressive surgery are broadly the same as those for hemorrhage. However, the clinical course tends to evolve more slowly. ^{15 , 16} Resection of the infarcted cerebellum itself is seldom helpful.

  
  
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  Cerebellar hemisphere infarction (due to distal posterior inferior cerebellar artery [PICA] occlusion) causing brainstem compression should be differentiated—by computed tomography (CT) and/or magnetic resonance imaging (MRI)—from brainstem destruction due to proximal ischemia, as the latter will not improve with surgery.

Trauma

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  Patients presenting with posterior fossa epidural hematoma (EDH) or acute subdural hematoma (SDH) who are awake and meet all of the following radiographic criteria can be managed conservatively, under close supervision: clot volume less than 10 mL, hematoma thickness less than 15 mm, and midline shift less than 5 mm. ¹⁷

  
  
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  Conversely, patients who present with a depressed level of consciousness, focal neurologic deficits, and/or ominous findings on CT scan (hydrocephalus, obliterated perimesencephalic cisterns, and/or a displaced fourth ventricle) are candidates for early surgical intervention. ^{1 , 3 , 6 , 18 , 19}

  
  
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  The indications for operative intervention in the setting of traumatic intracerebellar hematomas are similar to those for spontaneous hemorrhage (see above).

Radiographic Imaging

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  Noncontrast CT provides adequate initial imaging in the setting of trauma or hemorrhage.

  
  
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  MRI—in particular, diffusion-weighted imaging (DWI)—may be a useful adjunct in the setting of stroke to differentiate brainstem from cerebellar hemisphere ischemia.

  
  
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  If the initial CT scan reveals evidence of subarachnoid hemorrhage and/or blood in the fourth ventricle, preoperative vascular imaging (angiogram or CT angiogram) should strongly be considered to rule out an underlying aneurysm or arteriovenous malformation. The presence of an underlying vascular lesion may dictate a change in operative plan and/or preoperative endovascular intervention.

  
  
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  A patient with a known posterior fossa hematoma (traumatic or spontaneous) who is deteriorating rapidly should be taken to the operating room directly, without a repeat CT scan. The time required to complete an additional diagnostic study may not be worth the diagnostic yield in this setting.

  
  
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  Preoperative imaging (Fig. 5.1).

Ventriculostomy

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  The propensity of posterior fossa mass lesions to cause obstructive hydrocephalus means that a presurgical ventriculostomy is almost always mandatory before decompression. Failure to do so may result in massive herniation of the posterior fossa contents into the decompression, causing death on the operating table. The ventriculostomy should be inserted very rapidly to avoid delay in the deteriorating patient, and may be done as a part of the decompression (see below).

  
  
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  Occasionally, in moribund patients, or in those with smaller posterior fossa hemorrhagic lesions, a ventriculostomy may be placed, and the patient observed and re-scanned in 3 to 4 hours to determine if definitive surgery is indicated (e.g., if clinical improvement or enlargement of hematoma occurs).

  
  
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  Many authors advocate careful titration of the height of the drain (e.g., starting at 30 cm water and then lowering it by 5 cm water decrements every hour until 10 cm water is reached) in order to avoid “upward transtentorial herniation.” This may be more important in the setting of neoplastic posterior fossa mass lesions, where edema and a more protracted clinical course make this complication much more common.

Medication

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  The use of sedative-hypnotic agents should be avoided. Such medications may confound the clinical examination and precipitate respiratory depression.

  
  
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  A stat bolus dose of mannitol (0.5–1 g/kg intravenous piggyback [IVPB]) may be given if clinical deterioration occurs. Otherwise, a bolus is administered prior to skin incision in the operating room.

  
  
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  There is no role for preoperative antiepileptics unless there is concurrent supratentorial hemorrhage.

  
  
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  Prophylactic antimicrobial prophylaxis (the authors prefer cefuroxime) to cover gram-positive organisms is given per hospital protocol.

Positioning and Operative Field Preparation

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  To maintain adequate head flexion and rotation, a three-pinion head holder is essential. The cross bar should be padded to prevent pressure injury were slippage of the pins to occur (e.g., where the bridge of the nose or forehead would contact that cross bar).

  
  
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  For evacuation of a predominantly unilateral hematoma, the lateral park bench position—with the head turned to the contralateral side and flexed—is suitable. For subdural or extradural hematomas extending bilaterally, and for unilateral cerebellar infarctions (where extensive foramen magnum decompression is needed), the prone position is chosen. For trauma cases, we attempt to reduce/minimize cervical flexion during positioning if the cervical spine has not been cleared. The cervical collar is replaced after the procedure.

  
  
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  Either an iodine-based preparation or chlorhexidine/alcoholbased solution is used for skin preparation, taking care that the solution does not enter the eyes, especially in prone position. We use a transparent adhesive dressing film over the eyes to protect the cornea.

  
  
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  The incision is marked and infiltrated with 1% lidocaine with epinephrine 1:100,000.

Positioning (Fig. 5.2a, b)