Frontal Lobe and Pathology

The frontal lobe is the largest lobe in the brain.

It is seperated from the parietal lobe via the Central Sulcus and the temporal lobe by the Sylvian Fissure.

There are five functions of the frontal lobe

1. The Primary Motor Area (Pre-Central Gyrus)- this is the motor cortex is vital in producing contralateral voluntary movement.
2. Broca’s Area- Dominant hemisphere this is important in the expression of speech
3. Supplementary Motor Area MA- contralateral head and eye turning
4. Pre-Frontal Cortex- for Personality
5. Para-central lobule- cortical inhibition of bladder and bowel voiding
6. Frontal Eye Fields- conjugate movements of eyes, receiving inputs from the brainstem

Lesions of the Frontal Lobe May Manifest According to the origin of the pathology:

1. Pre-Central Gyrus- contralateral hemiplegia or monoplegia
2. Broca’s Area- Broca’s dysphasia depending on whether it is a dominant or non-dominant hemisphere
3. Supplementary Motor Area- Paralysis of head and eye movements to the opposite side, therefore the head and eye movements look in the SAME DIRECTION.
4. Pre-Frontal area- this involves the large majority of the frontal lobe rostral (anterior) to the motor cortex. They will often present with features if bilateral damage such as haemorrhage from an Anterior Communicating Artery aneurysm, global frontal atrophy as from dementia. There are three main syndromes but for this purpose we can suggest these patient will present with personality changes such as emotional lability, social disinhibition, indifference, apathy. Primitive reflexes such as grasping and  gait abnormalities e.g gait apraxia may persist
5. Paracentral lobule- Superior Frontal Gyrus (posterior aspect) can lead to loss of cortical inhibition of descending pathways to the bladder and bowel resulting in incontinence and faeces. This is a common component and clinical consideration in Normal Pressure Hydrocephalus

Clinical Examples

Frontal Tumour

Normal Pressure Hydrocephalus