Medicine – Features of Frontal Lobe Lesions

The frontal lobes are responsible for many higher functions, including personality, behaviour, motivation, planning, judgment, executive function, voluntary movement, speech production, and emotional control.

Frontal lobe lesions can therefore produce a broad range of abnormalities involving personality, language, behaviour, motor function, primitive reflexes, and executive ability.

1. Personality Change

One of the most characteristic features of frontal lobe disease is:

Personality change.

The patient may become:

Apathetic and withdrawn

or

Disinhibited and socially inappropriate.

The exact pattern depends partly on which frontal region is affected.

2. Apathy

Damage to medial frontal circuits can produce:

Apathy.

The patient may show:

Reduced initiative.

Loss of interest.

Reduced spontaneous speech.

Reduced emotional responsiveness.

Lack of motivation.

This may be mistaken for depression, although the underlying problem is impaired initiation and drive.

3. Abulia

A more marked reduction in motivation is called:

Abulia.

The patient remains awake and capable of movement but shows very little:

Spontaneous activity.

Speech.

Decision-making.

Initiative.

Severe bilateral medial frontal damage can progress toward:

Akinetic mutism.

4. Disinhibition

Orbitofrontal damage may cause:

Disinhibition.

The patient may become:

Impulsive.

Tactless.

Socially inappropriate.

Overfamiliar.

Irritable.

Sexually disinhibited.

They may understand social rules but fail to regulate behaviour appropriately.

5. Orbitofrontal Syndrome

An orbitofrontal lesion classically causes:

Disinhibition.

Poor judgment.

Impulsivity.

Emotional lability.

Socially inappropriate behaviour.

This reflects loss of normal inhibitory control over behaviour.

6. Broca Aphasia

A lesion involving the dominant inferior frontal gyrus, usually the left hemisphere, may cause:

Broca aphasia.

This is traditionally called:

Expressive aphasia.

7. Features of Broca Aphasia

Speech becomes:

Non-fluent.

Slow.

Effortful.

Agrammatic.

The patient may produce short phrases with omission of small connecting words.

For example, instead of saying:

“I went to the shop to buy food,”

they may say:

“Went shop… buy food.”

8. Comprehension in Broca Aphasia

Language comprehension is:

Relatively preserved, especially for simple sentences.

However, comprehension of complex grammatical structures may still be impaired.

This is why it is more accurate to describe Broca aphasia as:

Non-fluent aphasia

rather than simply “expressive aphasia.”

9. Repetition and Naming

In Broca aphasia:

Repetition is impaired.

Naming may be impaired.

The patient is often aware of the speech difficulty and may become frustrated.

10. Dominant Frontal Lobe

The dominant frontal lobe contributes to:

Speech production.

Verbal fluency.

Motor planning for speech.

A dominant frontal lesion may therefore cause:

Broca aphasia.

Reduced verbal output.

Apraxia of speech in some cases.

11. Abnormal Affective Reactions

Frontal lesions may alter emotional expression and regulation.

Patients may show:

Emotional lability.

Inappropriate laughter or crying.

Reduced emotional response.

Irritability.

Euphoria.

Indifference.

These abnormalities reflect disruption of frontal-limbic connections.

12. Emotional Lability

Emotional lability means rapid and poorly controlled changes in emotional expression.

The patient may:

Laugh inappropriately.

Cry easily.

Switch quickly between emotional states.

This can occur with frontal and other bilateral corticobulbar network lesions.

13. Difficulty Planning

The frontal lobes, especially the prefrontal cortex, are essential for:

Planning.

Organising.

Problem solving.

Decision-making.

Sequencing tasks.

Damage produces:

Executive dysfunction.

14. Executive Dysfunction

Executive dysfunction may cause difficulty with:

Planning a journey.

Managing finances.

Organising daily activities.

Solving unfamiliar problems.

Switching between tasks.

Following multistep instructions.

The patient may appear physically capable but function poorly in complex daily activities.

15. Reduced Motivation

Frontal lobe lesions can impair:

Initiation of behaviour.

The patient may need repeated prompting to:

Start a task.

Continue a task.

Speak.

Eat.

Dress.

This is particularly associated with medial frontal dysfunction.

16. Perseveration

Perseveration means inappropriate repetition of a previous:

Word.

Thought.

Action.

Response.

even when the task has changed.

17. Example of Perseveration

If a patient is asked to:

“Draw a circle,”

then later asked to:

“Draw a square,”

they may continue drawing circles.

This reflects impaired cognitive flexibility.

18. Why Perseveration Occurs

The frontal lobes allow a person to:

Stop an old response

and

Switch to a new strategy.

When frontal control is impaired:

The previous response continues despite changing circumstances.

19. Primitive Reflexes

Frontal lesions may cause the reappearance of:

Primitive reflexes.

These reflexes are present during infancy but are normally suppressed as the frontal lobes mature.

Damage can release them again.

20. Grasp Reflex

The grasp reflex is elicited by stroking or placing an object in the palm.

The patient automatically:

Grasps the object.

They may have difficulty releasing it voluntarily.

This suggests frontal lobe dysfunction, especially medial frontal involvement.

21. Rooting Reflex

The rooting reflex is triggered by touching the cheek or corner of the mouth.

The patient turns the mouth or head toward the stimulus.

This is normal in infants but abnormal in adults.

22. Pout Reflex

The pout reflex is produced by tapping around the lips.

The lips protrude or purse.

A marked response may occur in:

Frontal lobe disease.

However, isolated primitive reflexes are not highly specific and are more useful when combined with other frontal signs.

23. Palmomental Reflex

Another frontal release sign is the:

Palmomental reflex.

Scratching the thenar eminence causes contraction of the:

Ipsilateral mentalis muscle.

Like other primitive reflexes, it can be seen in frontal dysfunction but may also occur in older healthy adults.

24. Utilisation Behaviour

Some frontal lesions cause:

Utilisation behaviour.

The patient automatically uses objects placed in front of them even when not instructed to do so.

For example, they may:

Put on glasses placed on the table.

Pick up and use a comb automatically.

This reflects impaired suppression of stimulus-driven behaviour.

25. Imitation Behaviour

Patients with frontal dysfunction may automatically imitate:

Gestures.

Movements.

Actions

performed by the examiner.

This is called:

Imitation behaviour.

26. Motor Weakness

The frontal lobe contains the:

Primary motor cortex.

Therefore, a lesion involving the precentral gyrus can cause:

Contralateral upper motor neuron weakness.

The distribution depends on which part of the motor homunculus is affected.

27. Frontal Motor Cortex

The motor homunculus is arranged approximately as:

Leg medially.

Arm more superior-lateral.

Face most lateral.

Therefore, focal frontal lesions can produce selective weakness depending on location.

28. Anterior Cerebral Artery Lesions

The anterior cerebral artery supplies the medial frontal lobe.

An ACA stroke may therefore cause:

Contralateral leg-predominant weakness.

Abulia.

Reduced motivation.

Behavioural change.

Urinary incontinence in some cases.

29. Frontal Eye Fields

The frontal eye fields help control voluntary horizontal eye movements.

An acute destructive frontal eye field lesion may cause the eyes to deviate:

Toward the side of the lesion.

For example:

Left frontal lesion → eyes may deviate left.

This can be seen in large frontal strokes.

30. Urinary Incontinence

Medial frontal lesions can impair voluntary bladder control.

This may produce:

Urinary urgency

or

Incontinence.

It is particularly seen with bilateral or medial frontal dysfunction.

31. Frontal Gait Disorder

Medial frontal lesions may produce difficulty initiating walking.

The patient may have:

Short steps.

Gait freezing.

Magnetic gait-like features.

This can resemble the gait seen in:

Normal pressure hydrocephalus.

32. Dorsolateral Prefrontal Syndrome

Damage to the dorsolateral prefrontal cortex typically causes:

Executive dysfunction.

Features include:

Poor planning.

Reduced mental flexibility.

Difficulty problem-solving.

Impaired working memory.

Perseveration.

33. Medial Frontal Syndrome

Medial frontal damage tends to cause:

Apathy.

Abulia.

Reduced spontaneous activity.

Reduced speech.

Gait initiation problems.

Severe bilateral lesions may cause:

Akinetic mutism.

34. Orbitofrontal Syndrome

Orbitofrontal damage tends to cause:

Disinhibition.

Impulsivity.

Poor social judgment.

Emotional instability.

Inappropriate behaviour.

35. Frontal Lobe Seizures

Frontal lobe lesions may also produce:

Focal seizures.

These may be:

Brief.

Frequent.

Motor-predominant.

Sometimes bizarre in appearance.

Some occur mainly during sleep.

36. Causes of Frontal Lobe Lesions

Important causes include:

Stroke.

Brain tumour.

Traumatic brain injury.

Frontotemporal dementia.

Multiple sclerosis or other demyelinating disease.

Infection or inflammatory disease.

Hydrocephalus affecting frontal-subcortical pathways.

37. Frontotemporal Dementia

Frontotemporal dementia often affects frontal and anterior temporal networks.

Early features may include:

Personality change.

Disinhibition.

Apathy.

Loss of empathy.

Compulsive behaviour.

Dietary change.

Executive dysfunction.

Memory may be relatively less affected early than in Alzheimer disease.

38. Frontal Lobe Lesion – Note Form

Personality:

Apathy or disinhibition.

Language:

Broca aphasia with dominant inferior frontal lesion.

Affect:

Emotional lability or abnormal emotional responses.

Executive function:

Poor planning.

Poor judgment.

Reduced mental flexibility.

Difficulty solving problems.

Motivation:

Reduced initiative.

Apathy.

Abulia.

Primitive reflexes:

Grasp.

Rooting.

Pout.

Palmomental.

Perseveration:

Inappropriate repetition of the same response or action.

39. Frontal Regions – Note Form

Dorsolateral prefrontal cortex:

Executive dysfunction.

Poor planning.

Perseveration.

Impaired working memory.

Orbitofrontal cortex:

Disinhibition.

Impulsivity.

Poor social judgment.

Emotional lability.

Medial frontal cortex:

Apathy.

Abulia.

Reduced initiation.

Gait problems.

Urinary incontinence.

Dominant inferior frontal gyrus:

Broca aphasia.

40. Important Corrections to the Original Notes

Broca aphasia is better described as a non-fluent aphasia rather than simply “expressive aphasia.” Speech is effortful and agrammatic, while comprehension is relatively preserved.

Primitive reflexes such as grasp, rooting, and pout are called:

Frontal release signs.

They suggest loss of frontal inhibitory control but are not completely specific.

Difficulty planning or maintaining motivation represents two related but distinct frontal problems:

Executive dysfunction particularly with dorsolateral lesions.

and

Apathy/abulia particularly with medial frontal lesions.

Personality change can vary depending on lesion location:

Orbitofrontal → disinhibited.

Medial frontal → apathetic/abulic.

Dorsolateral → executive dysfunction.

Key Clinical Pattern

Think of the frontal lobe as:

PERSONALITY + PLANNING + SPEECH + MOTOR CONTROL + INHIBITION.

The classic patterns are:

ORBITOFRONTAL → DISINHIBITED.

MEDIAL FRONTAL → APATHETIC / ABULIC.

DORSOLATERAL → POOR PLANNING + PERSEVERATION.

DOMINANT INFERIOR FRONTAL → BROCA APHASIA.

And remember the classic frontal release signs:

GRASP + ROOTING + POUT.