Anatomy clinical correlates: Cerebral hemispheres

The cerebral hemispheres are two symmetrical halves of the brain that contain billions of neurons and their connections, forming an amazing network of cells which help govern our everyday actions. These cerebral hemispheres consist of the cerebral cortex, subcortical white matter, and gray matter masses called the basal ganglia found throughout the subcortical white matter. Due to the complexity of our brains, the clinical conditions affecting our cerebral hemispheres lead to a variety of abnormal and strange symptoms, so understanding the anatomy of the cerebral hemisphere is crucial in understanding these conditions.

Let’s start with lesions of the cerebral cortex, which is the superficial gray matter of our brains containing billions of neurons responsible for processing information. Depending on which part of the cortex these lesions occur in, it can cause different clinical manifestations.

First, there are lesions of the prefrontal cortex, which is an area responsible for the makeup of a person’s personality and governs social behaviour. So, prefrontal cortex lesions cause frontal lobe syndrome which generally result in personality changes, and can specifically cause problems with planning, initiative, judgment, and social behaviour. Individuals have difficulty making decisions, and may become impulsive and aggressive. Individuals can also exhibit socially unacceptable behavior, where they no longer restrain from saying or doing inappropriate things, and may also no longer care about their clothing and appearance.

Injury to the prefrontal cortex may also contribute to the reemergence of primitive reflexes, such as the grasp reflex, suckling reflex, and groping reflex. Bilateral damage of the prefrontal cortex may lead to incontinence, gait apraxia, and can even lead to akinetic mutism, where awake individuals lack the will or motivation to move or speak, but will follow you with their eyes in response to noise.

Next up, there are injuries to the frontal eye fields which can be found on the middle frontal gyrus - specifically, in Brodmann's area 8. Possible causes of lesions to the frontal eye fields include stroke involving the middle cerebral artery, brain tumors, or injury during neurosurgery.