Frontal Lobe Brain Injury

Original Editor - Wendy Walker

Lead Editors - Wendy Walker, Lucinda hampton, Aminat Abolade, Kim Jackson, WikiSysop and Claire Knott

Introduction

In evolutionary terms the frontal cortex has been the most recent to evolve, and the frontal lobes are the area of brain which has developed greatly in humans, differentiating us from other mammals. These lobes integrate the other brain areas, and are particularly responsible for higher level thinking and cognitive skills such as planning, evaluating likely outcomes, multitasking, performing risk assessment and the niceties of social interaction; it is the area of brain which deals in abstract concepts.

Anatomy

The Frontal Lobes account for approximately one third of human brain mass.

They lie at the front of the brain, anterior to the parietal lobes and superior to the temporal lobe.

Each frontal lobe (left and right) is generally considered to have several distinct divisions:

• Motor cortex
• Premotor cortex
• Supplementary motor cortex
• Prefrontal cortex
• Orbital cortex AKA frontal eye fields
• Broca's Area
  

Vascular Supply

Medial frontal lobe: anterior cerebral artery

Deep & lateral regions: superior division of middle cerebral artery

Function

The frontal lobe is the part of the brain which modifies and imposes constraints on reflexive behaviours, and this control develops as the infant brain grows and the frontal lobes become larger and more active.

• Motor cortex = voluntary movement
• Premotor cortex = storage of motor patterns & voluntary activities
• Prefrontal cortex = ability to concentrate; inhibition of reflexive behaviours; personality & emotional traits; abstract thinking
• Broca's Area = Motor control of speech    

Primary Motor Cortex

Input: Basal ganglia, thalamus, premotor cortex (in the frontal lobe), sensory cortex (in the parietal lobe)
Output: Motor fibres to spinal cord and brainstem, travelling in the corticospinal tract
Function: Movement

Pre motor Cortex

Input: Basal ganglia, thalamus, sensory cortex

Output: Primary motor cortex

Function: storage of motor programs, sensorimotor integration, facilitation of controlled, smooth movements

Supplementary Motor Cortex

Input: Thalamus, cingulate gyrus, sensory & prefrontal cortex

Output: Premotor cortex, primary motor cortex

Function: Intentional preparation for movement, procedural memory

Prefrontal Cortex

Function: working memory, executive functions including the ability to plan & implement (& monitor/evaluate) a series of goal-directed actions.

Frontal Eye Fields

Input: Parietal cortex, temporal cortex

Output: Caudate, superior colliculus, paramedian pontine reticular formation

Function: Control of voluntary scanning movements of the eye

Broca's Speech Area

Input: Wernicke's area

Output: Primary motor cortex

Function: Dominant hemisphere = speech production.  Non-dominant hemisphere = emotional & melodic component of speech

Pathology/Injury - Symptoms

It has been found that in traumatic brain injury contusions typically occur on the poles and the inferior aspects of the frontal lobes.

Disturbances of Motor Function

• Loss of fine  movements, strength & speed  [damaged area = primary motor cortex]
• Changes in voluntary gaze  [damage to frontal eye field]
• Changes in speech  [damaged area = Broca's speech area), usually slow, hesitant speech, difficulties in word finding, perseveration

3 Frontal Lobe Syndromes

Orbitofrontal syndrome = lack of inhibition

Frontal convexity syndrome = apathetic

Medial frontal syndrome = akinetic

Orbitofrontal syndrome

Patient demonstrates disinhibited, impulsive behaviour; difficulty in controlling their emotions; difficulty in maintaining concentration; lacking in judgement; failure to appreciate/anticipate consequences of their actions; can show euphoria, hypomania or grandiosity.

Orbitofrontal damage can also lead to abnormal sexual behaviour.

Frontal convexity syndrome

Patient shows disinterest and is apathetic; slowing of motor functions; unable to plan ahead; lacks motivation; lacks concern about the world around them.  

Medial frontal syndrome

Reduced movement; loss of sensation in lower limbs; urinary incontinence; occasional mutism; profound apathy; sometimes show indifference to thirst or hunger

References

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