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Temporal lobe lesions

Disturbance in function of the temporal lobe may be due to ischaemic or haemorrhagic damage as with a stroke, space occupying lesion, traumatic or related to epilepsy. It is a complex part of the brain dealing with many "higher functions" and so behaviour and intellect may be affected rather than gross motor skills.

Temporal lobe epilepsy is discussed elsewhere and this article will concentrate on neurological problems caused by temporal lobe deficits.

Aetiology: The commonest cause of temporal lobe lesions is stroke. Space occupying lesions may be primary tumours, benign or malignant, such as meningioma or metastatic carcinoma, most often from lung cancer or breast cancer. Trauma from head injury may be involved or surgical damage when removing a tumour from that region. Head injury often includes extradural haematoma and contracoup injuries. Surgery for intractable temporal lobe epilepsy is well established but follow up seems concerned with the alleviation of convulsions and heavy medication rather than the subtleties of temporal lobe function. Other pathologies such as multiple sclerosis can affect the temporal lobes although this is an unusual manifestation. Progressive deterioration of language can be part of a fronto-temporal lobe dementia. It presents earlier than Alzheimer's disease and about 50% have a family history that suggests an autosomal dominant inheritance.

Presentation: A stroke tends to produce a rapid onset of symptoms whilst a space occupying lesion will produce a more insidious onset. Whilst a hemiparesis is obvious to the patient and family, and will be recognised as such, the manifestations of temporal lobe lesions are more subtle and they may be interpreted as psychosis or dementia. It is the role of the doctor to unravel these strange presentations and to appreciate that it represents a structural lesion. Careful history, with attention to detail, is required, going back over history at times, during examination and remembering that some lesions will not be apparent to the patient and so he will not complain of them.¹ Some history from a third party can be useful.

There are 8 principal symptoms of temporal lobe damage:

• Disturbance of auditory sensation and perception
• Disturbance of selective attention of auditory and visual input
• Disorders of visual perception
• Impaired organization and categorization of verbal material
• Disturbance of language comprehension
• Impaired long-term memory
• Altered personality and affective behaviour
• Altered sexual behaviour

Manifestations of temporal lobe lesions:

• Disorders of auditory perception:
  • Lesions of the left superior temporal gyrus produce problems of speech perception with difficulty in discriminating speech and the temporal order of sounds is impaired.
  • Lesions of the right superior temporal gyrus produce prosody. Prosody is the study of the meter of verse. Here it means the rhythm of speech.
• Lesions of the right superior temporal gyrus can produce disorders of perception of music with inability to discriminate melodies.
• The inferior temporal cortex is responsible for visual perception and lesions produce inability to recognise faces,² called prosopagnosia.
• There may be disturbance of visual and auditory input selection. This presents as impairment of short term memory, also called working memory and judgement about the recency of events.
• The area is responsible for the organisation and categorisation of words and pictures. Impairment of this ability to categorise means reduced ability and fluency in listing categories.
• There may be difficulty using contextual information, in extracting information from the environment and using visual and social cues.
• The medial and inferior temporal cortex and hippocampus are responsible for memory. There is complete anterograde amnesia following bilateral removal of medial temporal lobes, including hippocampus & amygdala. There is diffculty recalling information. The left side is responsible for verbal material and the right for non-verbal memory such as faces, tunes and drawings. The difference between retrograde and anterograde amnesia is that retrograde amensia is loss of memory from before an event. It often happens with head injury with loss of memory leading up to that event although this is commonly gradually recovered. Anterograde amnesia is loss of memory between the event and the present time.
• There is a temporal lobe personality. There is an emphasis on trivia and the small details of daily life. There is egocentricity, pedantic speech, perseveration of speech, paranoia, religious preoccupations and a tendency to aggressive outbursts, especially after right temporal lobectomy. Perseveration is when there is a continuous but futile attempt to produce a word or perform an action long after others would have given up or tried a different approach.
• As well as behavioural change, temporal lobe lesions can present with visual field defects in the form of superior quadrant loss, sometimes called the "pie in the sky defect."
• Temporal lobe lesions may be associated with true hypersexuality, transvestite and transsexual behaviour.³ Stroke normally reduces libido but temporal lobe lesions can increase it.⁴ Lesions of the inferior temporal lobe have been reported to produce the Kluber-Bucy syndrome.

Examination: The problems of examining difficulties of speech and comprehension are discussed in dysarthria and dysphasia. In terms of recognising the ability to recall information or to recognise faces, it is complicated if there is impairment of speech. A strange or "temporal lobe personality" may be apparent but history from one close to the patient is more reliable and will attest to changes in personality. Accurate testing and ability to make an anatomical diagnosis may well be beyond the ability of most general practitioners when presented with such patients and the help of a neuropsychologist may be required.

If a stroke is suspected, check the cardiovascular system, including blood pressure, auscultation of the heart and carotid arteries.

A brief examination of the rest of the nervous system is required.

Investigations:

• Modern imaging studies can now localise lesions with great accuracy. MRI tends to be better than CT.
• If metastatic cancer is suspected a CXR is required.
• Visual field defects can be assessed by perimetry.
• A possible or certain diagnosis of stroke requires investigation as outined in stroke prevention.
• Referral to a neuropsychologist may still be useful to elucidate the precise nature of the problem and for help with management.

Management is along the lines of stroke rehabilitation.

Prognosis: Young people, especially children, have an ability to let one part of the brain take over the function of a damaged part but this is lost with increasing age. Hence young patients may regain some function but this is unlikely with advancing age.

References:

1. Takeda K; ;Rinsho Shinkeigaku. 2004 Nov;44(11):834-6.[abstract]
2. Milner B; Visual recognition and recall after right temporal-lobe excision in man.;Epilepsy Behav. 2003 Dec;4(6):799-812.[abstract]
3. Gautier-Smith PC; ;Rev Neurol (Paris). 1980;136(4):311-9.[abstract]
4. Monga TN, Monga M, Raina MS, et al; Hypersexuality in stroke.;Arch Phys Med Rehabil. 1986 Jun;67(6):415-7.[abstract]

Internet:

• Kirshner H Frontal and temporal lobe dementia; eMedicine; March 2005
• Long CJ in Neuropsychology & Behavioural Neuroscience. Brain-Behavior Relationships of anterior amd mid temporal cortex
• Joseph R memory tests- Immediate & Short Term Verbal Memory

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 2006.

Last issued 08 May 2006