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Frontal lobe lesions

The frontal lobes represent a large volume of the brain but the presentation of frontal lobe lesions can be very subtle. Neurological examination and even psychometric testing may miss the diagnosis. It is largely the higher functions and personality that are affected.

Epidemiology
Incidence Frontal lobe dementia is the 3^rd commonest form of dementia, after Alzheimer’s disease and multi-infarct dementia but it is very much less common than Alzheimer's.

Risk Factors Lesions can be vascular in origin (thrombotic, embolic or haemorrhagic), due to space occupying lesions (tumours or abscess) or traumatic. There may be other mechanisms like frontal dementia or multiple sclerosis. The effect will depend upon the exact location. In infants and young children brain damage results in adjacent areas taking over the function of the affected area but even a little later in life this ability fades and is lost. Most lesions occur in older people.

Presentation
Symptoms The patient often complains of remarkably little. It is those around who complain. Take the history from one who knows him well. Ask about developmental history, head injury, and social history including educational and personal attainments, work history, and substance abuse.

Signs Motor symptoms are fairly subtle:

• Loss of fine movement
• Loss of speed and strength in hand and limb movement
• Poor programming of movements
• Poor voluntary eye gaze

The higher functions are affected.

• Short term memory is impaired with easy distraction.
• Convergent thinking is when there is one correct answer and divergent when there are multiple correct answers. Frontal lobe damage impairs divergent thinking.
• Loss of spontaneous behaviour, like speaking and verbal fluency¹, impaired drawing and doodling, with general lethargy and initiation of daily routines.
• Impaired strategy formation and planning, especially in unfamiliar situations,
• There is inappropriate behaviour with difficulty using social cues and information to direct, control, or change personal behaviour.
• Inhibition impaired. This leads to perseveration (continuing to attempt a task that is obviously failing). They may confabulate.
• Behavioural changes include breaking rules and taking risks, not following task instructions and gambling. (Gambling involves assessing risk and outcome).
• Social and sexual behaviour inappropriate² or altered from previously. In social reasoning the left lobe is more important than the right³.
• Pseudodepression with psychomotor retardation, while the indifference is like "la belle indifference" of hysteria.
• Pseudopsychopathy (because of the lack of social inhibitions)
• Humour seems to decline with age but is more marked in frontal lobe lesions⁴.

Special techniques are required to examine frontal lobe function and find out how the patient now behaves compared with his previous performance.

Differential Diagnosis

• It may be mistaken for purely psychiatric disease.
• Check for syphilis and HIV, B12 deficiency and hypothyriodism.
• Dementia
• Trauma
• Alcoholism
• Stroke
• Substance abuse
• Developmental disorder
• Neglect

Investigations There are useful tests for Frontal Lobe Function but many will require a neuropsychologist. For this reason only very few will be briefly mentioned here. More detail is on the listed websites.

• Abstract thinking (if I have 18 books and two bookshelves, and I want twice as many books on one shelf as the other, how many books on each shelf?)
• Ask the patient to hold up one finger if the examiner holds up two, and two if the examiner holds up one. Test the patient to ensure understanding of the task. Give 10 trials. A failure to respond correctly (ie, echopraxia) suggests a lack of adequate response inhibition.
• Proverb and metaphor interpretation
• Rhythm tapping tasks
• Cognitive tasks include the word fluency test, in which a patient is asked to generate, in 1 minute, as many words as possible beginning with a given letter. (Normal around 15 depending upon education.)
• Serial subtraction of 7 from 100 they often find difficult to perform.

MRI is generally more sensitive than CT and may show infarction, haemorrhage, space occupying lesions, demyelination or atrophy. EEG often shows little of note. In frontal lobe dementia the EEG remains normal but CT or MRI will confirm lobar atrophy.

Anatomical diagnosis There are 3 different anatomical areas that give a characteristic picture:

• Medial frontal syndrome (akinetic)
• Paucity of spontaneous movement and gesture
  Sparse verbal output (repetition may be preserved)
  Lower extremity weakness and loss of sensation
  Incontinence
• Frontal convexity syndrome (apathetic)
• Apathy (occasional brief angry or aggressive outbursts common) is characterized by reduced spontaneous activity that ranges from akinetic mutism to transient abulic hypokinesia.
  Indifference
  Psychomotor retardation
  Motor perseveration and impersistence
  Discrepant motor and verbal behaviour
  Poor word list generation.

• Orbital frontal syndrome (disinhibited)
• Disinhibited, impulsive behaviour (pseudopsychopathic)
  Inappropriately jocularor euphoric but rather empty and not like mania.
  Emotional lability
  Poor judgment⁵ and insight
  Distractibility

Management
Non-Drug They are very difficult to manage and may need residential care. Lack of inhibition can be a particular problem.
Drugs No drugs directly affect the frontal lobes.
Surgical Removal of space-occupying lesions in this area can be very difficult.

Associated diseases

• Focal epilepsy can originate from the frontal lobes. Features include frequent clusters of brief seizures, with sudden onset and cessation. The accompanying motor features may be bizarre and if the EEG is normal, they may be diagnosed as hysterical pseudoseizures.
• There is growing evidence that frontal lobe dysfunction plays a part in the development of schizophrenia⁶.
• Frontal lobe dementia (Pick's disease) is more common in females. It may be inherited as an autosomal dominant gene, although most cases are sporadic. Abnormalities of behaviour, emotional changes, and aphasia are frequent. Relationships deteriorate, insight is lost early, and the jocularity of frontal lobe damage may suggest mania. Aphasia causes word-finding difficulties and empty, flat, nonfluent speech. Cognitive changes become apparent with time. These include memory disturbance and impairment on frontal lobe tasks. Eventually there are extrapyramidal signs, incontinence, and widespread cognitive decline.
• "Executive processes" play a role in cognitive functions like attention and working memory, and appear to be disrupted in alcoholism. The picture is very similar to a frontal lobe lesion⁷.
• Impairments in problem-solving occur with left anterior frontal lobe lesions, Tourette’s syndrome and Asperger’s syndrome ⁸.

Prognosis Prognosis depends upon cause but little is amenable to treatment. Decline can continue over many years.

Prevention There is no known prevention.

References Used

1. Henry JD, Crawford JR; A meta-analytic review of verbal fluency performance following focal cortical lesions.;Neuropsychology 2004 Apr;18(2):284-95.[abstract]
2. Berlin HA, Rolls ET, Kischka U; Impulsivity, time perception, emotion and reinforcement sensitivity in patients with orbitofrontal cortex lesions.;Brain 2004 May;127(Pt 5):1108-26. Epub 2004 Feb 25.[abstract]
3. Goel V, Shuren J, Sheesley L, et al; Asymmetrical involvement of frontal lobes in social reasoning.;Brain 2004 Apr;127(Pt 4):783-90. Epub 2004 Feb 19.[abstract]
4. Shammi P, Stuss DT; The effects of normal aging on humor appreciation.;J Int Neuropsychol Soc 2003 Sep;9(6):855-63.[abstract]
5. Gomez-Beldarrain M, Harries C, Garcia-Monco JC, et al; Patients with right frontal lesions are unable to assess and use advice to make predictive judgments.;J Cogn Neurosci 2004 Jan-Feb;16(1):74-89.[abstract]
6. Quintana J, Wong T, Ortiz-Portillo E, et al; Prefrontal-posterior parietal networks in schizophrenia: primary dysfunctions and secondary compensations.;Biol Psychiatry 2003 Jan 1;53(1):12-24.[abstract]
7. George MR, Potts G, Kothman D, et al; Frontal deficits in alcoholism: an ERP study.;Brain Cogn 2004 Apr;54(3):245-7.[abstract]
8. Channon S; Frontal lobe dysfunction and everyday problem-solving: social and non-social contributions.;Acta Psychol (Amst) 2004 Feb-Mar;115(2-3):235-54.[abstract]

Internet and Further Reading

• Psychopathology of Frontal Lobe Syndromes
• Overview of the condition with more on examination

Acknowledgements EMIS is grateful to the Mentor authoring team for writing this article. The final copy has passed peer review of the independent Mentor GP authoring team. ©EMIS 2004.

Last issued 02 Nov 2005