Specific Neuro-psychiatric syndromes

These are organic brain disorders that do not present with global cognitive impairment.

Focal cerebral syndromes

Shared features of these conditions are that they: -

• Show selective impairment of cognitive function
• May have demonstrable specific or localised brain pathology.

In most people, the left side of the brain is dominant i.e. primarily responsible for language skills and the non-dominant right side is primarily responsible for visuo-spatial skills. Put simply, the left side of the brain is dominant in right-handed people.

The localisation of brain function is a complex area, but some generalisations can be made.

• Pre frontal area
• Dominant parietal lobe
• Non-dominant parietal lobe
• Pre-central gyrus
• Temporal lobe
• Occipital lobe
• Corpus callosum
• Thalamus, basal ganglia and brainstem

Pre-frontal area

Pathology of the frontal lobe may result in:

• Dysexecutive syndrome - that is difficulties with problem solving, reasoning, mental abstraction, impulsivity, distractibility and failure to persevere with the task in hand.
• Orbitofrontal syndrome - that is a change in behaviour characterised by a lack of empathy and emotional warmth; disinhibition, irresponsibility; stereotypical and ritualised behaviours
• Amotivational states - that is unable to move or speak spontaneously, preferring to sit in a chair staring blankly into space.

Although attention, which is the ability to focus and sustain attention is a function of the frontal lobe, there are other areas of the brain involved, and the commonest causes of loss of attention are diffuse brain insults, such as head injury or delirium.

Dominant parietal lobe

Pathology of the dominant parietal lobe may result in language disorders, which may affect the ability to speak (Aphasia), read (Dyslexia) or write (Agraphia).

Aphasias include:

• Expressive aphasia (Broca’s aphasia) - Reduced fluency of speech with comprehension relatively preserved. Language is reduced to a few disjointed words and there is a failure to construct sentences i.e. the person knows what they want to say but cannot get the words out.
• Receptive aphasia (Wernicke’s aphasia) - Language is fluent but the words are incorrect. This varies from the insertion of a few incorrect or non-existent words to language that is not understandable with wholly non-existent words i.e. the person does not understand what they are saying.
• Global aphasia (anomic aphasia or amnestic aphasia) - Combination of expressive and receptive aphasia so that the person can neither speak, understand language, read or write. It is the most common form of aphasia after a severe left hemisphere stroke.
• Nominal aphasia - Difficulty naming familiar objects for example, a watch.

Dyslexia

People with acquired dyslexia have difficulties in keeping with their type of aphasia. For example, people with expressive aphasia have trouble with grammatical aspects of words or reading whilst those with receptive aphasia will struggle to understand the meaning of words in printed form.

Agraphia

People with agraphia have difficulties in keeping with their type of aphasia. For example people with expressive aphasia will make errors in writing syntax.

Apraxia

Pathology of the non-dominant parietal lobe may result in apraxia, that is loss of ability to carry out skilled motor tasks that cannot be explained by a disorder of motor control (weakness or ataxia), sensory disturbance or a global impairment of cognition.

Apraxias include:

• Limb kinetic apraxia is the loss of fine motor control that may occur after a stroke. The person cannot manage tasks involving fine motor control, for example, tying a shoelace or buttoning a shirt.
• Ideational (conceptual) apraxia is the inability to conceive or formulate an action either spontaneously or on demand
• Ideomotor (production) apraxia is the inability to carry out an action despite knowing and remembering the plan of action.
• Constructional apraxia is the inability to put things together, like jigsaw puzzles, or draw and copy line drawings.
• Dressing apraxia is the inability to dress properly.

Non-dominant parietal lobe

Pathology of the non-dominant parietal lobe may result in visuo-spatial and perceptive disorders, which include: -

• Mis-reaching for visually guided targets, tripping on steps or colliding with furniture.
• Spatial neglect involves neglect of all sensory information (visual, tactile and auditory) from the side opposite to the brain pathology. This is usually seen as a person with a right-sided stroke who is unable to acknowledge the left side of the body and may deny that this is their own.
• Right-left disorientation, that is the inability to differentiate between left and right, for example the person may not be able to touch right ear with right hand.

Agnosia is the inability to understand the significance of sensory stimuli despite normal intellectual and sensory function.

An agnosia may be:

• visual, for example unable to recognise a photograph of a close relative
• auditory, for example unable to recognise the doorbell
• sensory, for example unable to recognise objects such as coins placed in hand
• olfactory, for example unable to recognise familiar smells like coffee.

Pre-central gyrus (within the parietal lobe)

Pathology of the pre-central gyrus may produce expressive aphasia.

Temporal lobe

Pathology of the temporal lobe may produce memory loss, hallucinations (auditory and visual), seizures, decreased concentration and attention, mood problems and receptive aphasia.

Occipital lobe

Pathology of the occipital lobe may produce:

• Visual field loss - for example, pathology of the left occipital lobe will cause a right homonomous hemianopia i.e. loss of the right visual field.
• Cortical blindness - that is complete blindness. Some people with cortical blindness deny that they have any visual problem at all (Anton’s syndrome or visual anosagnosia)
• Visual disorientation
• Complex visual hallucinations.

Corpus callosum

Pathology of the corpus callosum is likely to cause acute and severe intellectual impairment

Thalamus, basal ganglia and brainstem

Pathology in these structures may present in a variety of ways. Personality, intellect (decreased IQ), cognitive ability and information processing can all be affected.