Surgical evacuation of cerebellar hematoma The surgical evacuation of cerebellar hematoma is a generally accepted treatment and is an urgent matter because of the proximity of the mass to the brainstem and the risk of abrupt respiratory failure. Also, hydrocephalus from compression of the fourth ventricle often complicates the clinical picture and further raises intracranial pressure (St. Louis et al). As a rule, a cerebellar hematomas less than 2 cm in diameter leaves most patients awake and infrequently leads to deterioration, therefore generally not requiring surgery. Hematomas that are 4 cm or more in largest diameter, especially if located in the vermis, pose the greatest risk, and some surgeons have recommended evacuation of lesions of this size no matter what the clinical status of the patient. In determining the need for surgical evacuation, we have been guided by the patient’s state of consciousness, the mass effect caused by the clot as visualized on imaging (particularly the degree of compression of the quadrigeminal cistern, as pointed out by Taneda and colleagues), and the presence or absence of hydrocephalus. Assessment may require daily or even more frequent CT. The patient who is stuporous or displays arrhythmic breathing is best intubated and brought to the operating room within hours or sooner. Once coma and pupillary changes supervene, few patients survive, even with surgery; however, rapid medical intervention with mannitol and hyperventilation, followed by surgical evacuation of the clot and drainage of the ventricles within hours of the onset of coma has been successful in some cases. Patients who are drowsy and those with hematomas of 2 to 4 cm in diameter in the cerebellar hemisphere pose the greatest difficulty in determining if, and when, surgery is advisable. If the level of consciousness is fluctuating or if there is obliteration of the perimesencephalic cisterns, particularly if coupled with hydrocephalus, the risk of surgery may be lower than the risk of a sudden deterioration. In only a very limited number of patients have we found it practical to perform only drainage of the enlarged ventricles, although some groups still favor this procedure and eschew a posterior fossa operation. Evacuation of the clot in our experience has been more important than reduction of the hydrocephalus.