Key Issues To Address Prior To Hemicraniectomy

Evidence that hemicraniectomy reduces mortality is largely derived from uncontrolled case series and retrospective studies. Early animal studies revealed that trephination surgery, a form of hemicraniectomy in rats, reduces the seven-day mortality from 35% in the nonsurgical group to almost 0% in the surgical group (15,16). Neurologic behavior and infarct volume were favorable in those treated with ultra-early surgery within four hours of occlusion, confirming the importance of early intervention. Compared to control groups, hemicraniectomy in rats increases perfusion in the cortex and reduces the infarct volume, as shown by MRI (17).

Hemicraniectomy can also be combined with other techniques that can synergistically help to reduce brain edema. Comparison of moderate hypothermia to hemicraniectomy in massive cerebral infarctions reveals that hemicraniectomy is, in fact, better, with no difference in intensive medical treatment or duration of stay in the neurologic intensive care unit. In one retrospective study, the mortality rate was 47% for the hypothermia group versus 12% for the hemicraniectomy group (18). In a case series that combined hemicraniectomy with resection of infarcted tissue, 10 of 12 patients who underwent the procedure survived, 5 had independent or moderate disability, and 5 were left with severe disability. The mortality rate was 16%, but the disability rate was high at 41%, compared to other published case reports (19). Table 1 contains a review of all of the current hemicraniectomy trials.

A number of issues arise when one considers hemicraniectomy for massive cerebral infarctions, as discussed below.

Hemicraniectomy Following Large Hemispheric Infarctions

Hemicraniectomy is usually considered when unequivocal clinical and radiological signs suggest impending brain edema and when all other medical measures have failed. Common predictors of brain edema following large hemispheric infarction include young age, nausea and vomiting in the first 24 hours of admission, NIHSS of >15 for right hemisphere MCA infarction and >20 for left hemisphere MCA infarction, early hypodensity on CT scan, midline shift of more than 10 mm at the septum pellucidum level, and early hypodensity that involves more than 50% of the MCA territory (6). Some authors advocate repeating CT scan within 6 to 12 hours for those at high risk for brain edema (4). Evidence of anteroseptal shift >5 mm on follow-up CT is strongly associated with fatal outcome and might act as an important warning sign of further shift to come (8). Early hemicraniectomy should be considered before brain herniation and irreparable brain damage occurs. Women with malignant MCA infarction had worse outcomes than men in one retrospective study (20) . The presence of vascular territory involvement beyond the MCA territory also serves as a marker of progression (8). Anterior choroidal artery infarction involving the uncus and hippocampal head can predispose to a greater degree of herniation and secondary brain stem compression. MRI offers advantages in detecting malignant MCA

Figure 3 Decompressive hemicraniectomy and duraplasty in a 44-year-old male following carotid dissection from motor vehicle accident. The ischemic/infarcted brain tissue in the right hemisphere has room for herniation outward and prevents downward displacement of vital structure.

infarction by allowing assessment of volumes of diffusion-weighted and perfusion-weighted abnormality. A diffusion-weighted imaging abnormality of median volume >145 mL 14 hours from onset was associated with a malignant course, with 100% sensitivity and 94% specificity (21). An apparent diffusion coefficient <80%, involving greater than 82 mL of brain tissue less than 6 hours from onset had similar high sensitivity and specificity for malignant course (22). Serum markers, such as S100B, have also been shown to predict a malignant course of MCA infarction (23). Unfortunately, no single parameter can signal that malignant MCA infarction will definitely occur. A combination of clinical and imaging prognostic factors should be present before hemicraniectomy is contemplated.

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