Frontal Lobe Syndrome

Excerpt

Neuroanatomically, the frontal lobe is the largest lobe of the brain lying in front of the central sulcus. It is divided into 3 major areas defined by their anatomy and function. They are the primary motor cortex, the supplemental and premotor cortex, and the prefrontal cortex. Damage to the primary motor, supplemental motor, and premotor areas lead to weakness and impaired execution of motor tasks of the contralateral side. The inferolateral areas of the dominant hemisphere are the expressive language area (Broca area, Brodmann areas 44 and 45), to which damage will result in a non-fluent expressive type of aphasia. Frontal lobe syndrome, in general, refers to a clinical syndrome resulting from damage, and impaired function of the prefrontal cortex, which is a large association area of the frontal lobe. The areas involved may include the anterior cingulate, the lateral prefrontal cortex, the orbitofrontal cortex, and the frontal poles.

Frontal lobe syndrome is a broad term used to describe the damage of higher functioning processes of the brain such as motivation, planning, social behavior, and language/speech production. Although the etiology may range from trauma to neurodegenerative disease, regardless of the cause frontal lobe syndrome poses a difficult and complicated condition for physicians. Classically considered unique among humans, the frontal lobes are involved in a variety of higher functioning processing, such as regulating emotions, social interactions, and personality. The frontal lobes are critical for more difficult decisions and interactions that are essential for human behavior. However, with the spread of neurosurgery and procedures such as lobotomy and leucotomy for the treatment of psychiatric disorders, a variety of cases have illustrated the significant behavioral and personality changes due to frontal lobe damage. Harlow first described this collection of symptoms as "frontal lobe syndrome" after his research on the famous Phineas Gage who suffered a dramatic change in behavior as a result of trauma. Thus, an abnormality in the frontal lobe could dramatically change not only processing but personality and goal-oriented directed behavior.

Prior research has sought to identify the major areas where lesions may occur to cause the behavioral changes in frontal lobe disorders.

Ventromedial Orbitofrontal Cortex

Commonly known to cause “frontal lobe personality”, lesions in the orbitofrontal areas classically cause dramatic changes in behavior leading to impulsivity and a lack of judgment. Lesions usually found in Broadmann’s Areas 10, 11, 12, and 47 are associated with a loss of inhibition, emotional lability, and inability to function appropriately in social interactions. The most popular case involving a lesion in this area is the case of Phineas Gage who had major behavioral changes after his trauma. However, in a study by Tranel and Damasio et al., a variety of other etiologies such as stroke and neoplasms may cause “frontal lobe personality.”

Anterior Cingulate and Dorsolateral Syndromes

Lesions in the areas around Brodmann areas 9 and 46 may cause deficits within working memory, rule-learning, planning, attention, and motivation. Recent studies have reinforced that DLPFC is critical for working memory function and in particular for monitoring and manipulating the content of working memory. DLPFC may also affect attention as several cases have documented patients complaining of attentional deficits after brain trauma. There are also psychiatric implications due to injury to DPFMC. Previous studies have researched how lesions in the DLPFC may cause "pseudo-depressive" syndrome associated with DLPFC associated with a loss of initiative, decreased motivation, reduced verbal output, and behavioral slowness (abulia). Other processing issues include rule learning, task switching, planning/ problem solving, and novelty detection and exogenous attention. The anterior cingulate cortex is important for the motivation behind attention, but may also be involved in a variety of psychiatric disorders such as depression, post-traumatic stress disorder (PTSD), and obsessive-compulsive disorder (OCD).

A new area of research within the dorsolateral frontal cortices revolves around "intuition." The frontal lobes can communicate with the limbic system and association cortex. In turn, this emotional influence is associated with abstract decisions to create more efficient or “intuitive” decisions in a short span of time.