Tuesday, 19 January 2010

Injury to the Brain. - Agnosia

What is Agnosia?

Agnosia is a rare disorder characterised by an inability to recognise and identify objects or persons despite having knowledge of the characteristics of the objects or persons. People with agnosia may have difficulty recognising the geometric features of an object or face or may be able to perceive the geometric features but not know what the object is used for or whether a face is familiar or not.

Agnosia can result from strokes, dementia, developmental disorders, or other neurological conditions. It typically results from damage to specific brain areas in the occipital or parietal lobes of the brain where damage to, or degeneration of these areas of the brain that integrate perception, memory, and identification is the cause. Discrete brain lesions can cause different forms of agnosia, which may involve any sense. Typically, only one sense is affected. Examples are hearing (auditory agnosia, the inability to identify objects through sound such as a ringing telephone), taste (gustatory agnosia), smell (olfactory agnosia), touch (tactile agnosia), and sight (visual agnosia).

Other forms of agnosia involve very specific and complex processes within one sense. For example, prosopagnosia is the inability to identify well-known faces, including those of close family and friends, or to otherwise distinguish individual objects among a class of objects, despite the ability to identify generic facial features and objects.

Anosognosia often accompanies damage to the right, non dominant parietal lobe. Patients deny their deficit, insisting that nothing is wrong even when one side of their body is completely paralysed. When shown the paralysed body part, patients may deny that it is theirs. In an often related phenomenon, patients ignore the paralysed or desensitized body parts (hemi-inattention) or the space around them (hemineglect). Hemineglect most often involves the left side of the body.

Lesions to the occipital and temporal lobes may cause an inability to recognize familiar places (environmental agnosia), visual disturbances (visual agnosia), or colour blindness (achromatopsia). Right-sided temporal lesions may cause an inability to interpret sounds (auditory agnosia) or impaired music perception (amusia).

Is there any treatment?

Mainstream treatment is generally symptomatic and supportive of the individual sufferer. Snowdrop however are very aware that the brain is interconnected in very complex ways and has a high degree of plasticity and often, improvement in functioning in one area of the brain can positively influence the functioning of other areas. We therefore offer general stimulation programmes to sufferers of agnosia. For more details contact Snowdrop on info@snowdrop.cc.