Examination of the cognitive state is necessary to diagnose organic brain disorders, such as delirium and dementia. Poor concentration, confusion and memory problems are the most common subjective complaints. Clinical testing is a screening of cognitive functions, which may suggest the need for more formal psychometry. A premorbid estimate of intelligence can be made from asking the patient the final year level of education and the highest qualifications or skills achieved.

Testing can be divided into tests of diffuse and focal brain functions.

Diffuse functions

Orientation in time, place and person. Consciousness can be defined as the awareness of the self and the environment. Clouding of consciousness is more accurately a fluctuating level of awareness and is commonly seen in delirium.

Attention is tested by saying the months or days backwards.

Verbal memory. Ask the patient to repeat a name and address with 10 or so items, noting how many times it takes to recall it 100% accurately (normal is 1 or 2) (immediate recall or registration).

Ask the patient to try to remember it and then ask it of them again after 5 minutes (0 or 1 error is normal) (short-term memory).
Long-term memory. Ask the patient to recall the news of that morning or recently. If they are not interested in the news, find out their interests and ask relevant questions (about their football team or favourite soap opera). Amnesia is literally an absence of memory and dysmnesia indicates a dysfunctioning memory.

Focal functions

Frontal, temporal and parietal function tests. Frontal lobe skills are difficult to test at the bedside. Note any disinhibited behaviour not explained by another psychiatric illness, such as mania. Sequential tasks are tested by asking the patient to alternate making a fist with one hand at the same time as a flat hand with the other. Ask the patient to tap a table once if you tap twice and vice versa. Note any motor perseveration whereby the patient cannot change the movement once established. Observe for verbal perseveration, in which the patient repeats the same answer as given previously for a different question. Abstract thinking is measured by asking the meaning of common proverbs, a literal meaning suggesting frontal lobe dysfunction, assuming reasonable premorbid intelligence.

Box 22.4 Hallucination

An hallucination is defined as a perception in the absence of a stimulus. It is: a false perception and not a distortion perceived as inhabiting objective space perceived as having qualities of normal perception perceived alongside normal perceptions independent of the individual’s will.

• Illusions are misperceptions of external stimuli and are most likely to occur when the general level of sensory stimulation is reduced.
• Hallucinations. Healthy people occasionally experience hallucinations, such as in normal grief, or during the transition between sleeping and waking (hypnagogic and hypnapompic). Hallucinations can be elementary (e.g. bangs, whistles) or complex (e.g. faces, voices, music), and may affect any of the perceptions: auditory, visual, tactile, gustatory, olfactory or of deep sensation.
• Pseudohallucinations are usually auditory, and are either true externally sited hallucinations, but with insight into their imaginary nature, or are sited within internal space (e.g. ‘I heard a voice in my head speak to me’). They can occur in mood disorders and do not indicate a psychosis.
• Depersonalization is a change in self-awareness such that the person feels unreal or detached from their body. The individual is aware, however, of the subjective nature of this alteration.
• Derealization is the unpleasant feeling that the external environment has become unreal and/or remote; patients may describe themselves as though they are in a dream-like state. Both this and depersonalization can occur in healthy people when they are tired, after sensory deprivation and when using hallucinogenic drugs. They also occur in anxiety disorders, schizophrenia and temporal lobe epilepsy.
• Déjà vu is a sudden familiarity with a situation or event as having been encountered before when it is in fact novel.
• Jamais vu is the reverse experience when there is failure to recognize a situation or event that has been encountered before. Déjà vu experiences occur in healthy people as well as in extreme anxiety states. Both types of experience can occur in temporal lobe epilepsy.
• Increased sensitivity of perceptions, such as photosensitivity and phonosensitivity, occurs in anxiety disorders (e.g. increased sensitivity to the neon strip-lights and noise in a supermarket in agoraphobia) as well as neurological disorders such as migraine.

This is a complex network of structural proteins which regulates not only the shape of the cell, but also its ability to traffic internal cell organelles and even move in response to external stimuli. The major components are microtubules, intermediate filaments and microfilaments.

• Microtubules. These are made up of two protein subunits, α and β tubulin (50 kDa), and are continuously changing length. They form a ‘highway’, transporting organelles through the cytoplasm. There are two motor microtubule-associated proteins – dynein and kinesin – allowing antegrade and retrograde movement. Dynein is also responsible for the beating of cilia. During interphase the microtubules are rearranged by the microtubule-organizing centre (MTOC), which consists of centrosomes containing tubulin and provides a structure on which the daughter chromosomes can separate. Another protein involved in the binding of organelles to microtubules is the cytoplasmic linker protein (CLIP). Drugs that disrupt the microtubule assembly (e.g. colchicine and vinblastine) affect the positioning and morphology of the organelles. The anticancer drug paclitaxel causes cell death by binding to microtubules and stabilizing them so much that organelles cannot move, and thus mitotic spindles cannot form.
• Intermediate filaments. These form a network around the nucleus and extend to the periphery of the cell. They make cell-to-cell contacts with the adjacent cells via desmosomes, and with basement matrix via hemidesmosomes . Their function appears to be in structural integrity; they are prominent in cellular tissues under stress. The intermediate filament fibre proteins are specific to the embryonic lineage of the cell concerned, for example keratin intermediate fibres are only found in epithelial cells whilst vimentin is only found in mesothelial (fibroblastic) cells.
• Microfilaments. Muscle cells contain a highly ordered structure of actin (a globular protein, 42-44 kDa) and myosin filaments, which form the contractile system. These filaments are also present throughout the non-muscle cells as truncated myosins (e.g. myosin 1), in the cytosol (forming a contractile actomyosin gel), and beneath the plasma membrane. Cell movement is mediated by the anchorage of actin filaments to the plasma membrane at adherent junctions between cells. This allows a non-stressed coordination of contraction between adjacent cells of a tissue. Similarly, vertical contraction of tissues is anchored across the cell membrane to the basement matrix at focal adhesion
  junctions where actin fibres converge . Actin-binding proteins (e.g. fimbria) modulate the behaviour of microfilaments, and their effects are often calcium-dependent. The actin-associated proteins can be tissue type specific, for example actin-binding troponin is a complex of three subunits and two of these have isomers which are only found in cardiac muscle. Cardiac troponin I and T are released into the blood circulation after the onset of a myocardial infarction.

Alterations in the cell’s actin architecture are also controlled by the activation of small ras-like GTP-binding proteins rho and rac. These are involved in rearrangement of the cell during division, and thus dysfunctions of these proteins are associated with malignancy.