A true anatomical hemispherectomy is when all four lobes of one hemisphere of the cerebral cortex are removed in their entirety. They may be removed “en bloc” (all together) or in pieces. Because of where they are located within the brain, the amygdala and hippocampus on the affected side are removed. Sometimes the surgeon removes the thalamus and basal ganglia on the affected side as well. Technically, this is the least complicated of all the hemispherectomy procedures.
Anatomical hemispherectomy is often used today in many surgical facilities, usually for cases such as hemimegalencephaly where functional hemispherectomy can sometimes be unsuccessful.
There are significant short- and long-term complications that are associated with this procedure:
- Hydrocephalus: Hydrocephalus is a common side effect of anatomical hemispherectomy, with this study of 690 patients finding it in 30% of cases. Hydrocephalus is a risk throughout the lifespan, with 27% of children developing hydrocephalus three or more months after surgery;
- Superficial hemosiderosis is an extremely rare condition caused by chronic iron deposits on brain tissue. This was reported as a late complication of anatomical hemispherectomy in the early research papers. Blood product in the cerebrospinal fluid, whether left behind from the surgery or caused by blood leaking from tiny rips and tears in capillaries that can occur over time due to brain shift or dislodging of the hemisphere, is one possible cause of this condition. Symptoms of superficial hemosiderosis include gait imbalance, progressive loss of hearing which sometimes begins as ringing of the ears (tinnitus), vertigo, and other symptoms. Because the delayed mortality rate was reported as high as 40% for those with superficial hemosiderosis after hemispherectomy, anatomical hemispherectomy was largely abandoned in the early 1970s by many facilities. It is now believed that the high mortality rate may have been due to untreated hydrocephalus rather than superficial hemosiderosis in many of the early cases. Superficial hemosiderosis has not been reported in medical literature in over 30 years; however, there are anecdotal reports from parents of adults who had childhood anatomical hemispherectomy. It has also been reported many years after functional hemispherectomy;
- Brain shift into the resection cavity, microvascular tearing, and dislodging of the remaining hemisphere. The incidence of these risks is unknown.