A neural anomaly that develops only in seldom situations, agnosia is characterised by the loss of capabilities to comprehend sensory perceptions, like confusion in identifying common things, familiar people, noises, odours, tastes such as in ageusia and forms.

Also Read: Ageusia: Causes, Symptoms And Treatment

Derived from the Greek word agnosia meaning ignorance, this neurological illness occurs due to brain damage, in the specific sections of the parietal, temporal or occipital lobe. These regions of the cerebrum within the skull are responsible for developing cognitive functions, by safeguarding memories associated with sights, objects, sounds, for the smooth functioning of the sense of vision, touch and hearing. However, people with agnosia do not exhibit any structural damage to the sense organs – eyes, nose, ears, tongue, skin; nor do they suffer from memory loss. In most cases, agnosia hampers the relay of signals only in one specific information fragment in the brain, similar to situations of brain fog. Thus, people with agnosia can otherwise see, hear, communicate and think normally with other individuals as well as their surroundings.

Read on, to understand the causes, types, symptoms, diagnosis and treatment of agnosia.

Causes Of Agnosia

Agnosia is prompted by damage or decay in the segments of the brain wherein the tasks of storing sensory data, retention of language and memory take place, i.e. the parietal, occipital and temporal lobes.

Prominent injuries to the nerve cells comprising grey matter trigger agnosia, including stroke, encephalitis, dementia, brain cancer and trauma to the head.

Also Read: Stroke/Cerebrovascular Accident: Causes, Symptoms And Treatment

Types And Symptoms

Agnosia is categorised into three main types, as visual, auditory and tactile.

Visual Agnosia:

This brain-linked health anomaly arises when the nerve signalling pathways connecting the occipital lobe to the temporal lobe, parietal lobe are incapacitated. Since the occipital lobe processes visual signs from external objects and the temporal, parietal lobes assist in perceiving that data accurately, this, in turn, hampers optimal vision and eyesight, like in situations of presbyopia.

The numerous forms of visual agnosia consist of apperceptive visual agnosia, associative visual agnosia, prosopagnosia (face blindness), achromatopsia (colour blindness), agnosic alexia (pure alexia), akinetopsia (motion blindness).

Auditory Agnosia:

Auditory agnosia, known as auditory verbal agnosia or pure word deafness, occurs due to lesions in the right-sided portion of the temporal lobe. It presents in the form of the afflicted person being unable to distinguish well-acquainted voices or comprehend commonly spoken words.

The most frequently reported cases of auditory agnosia are of pure word deafness and phonagnosia.

Tactile Agnosia:

Wounded areas in the parietal lobe result in failure to correctly identify objects by means of touching them.

A common kind of tactile agnosia is autotopagnosia, wherein all systemic functions proceed normally, but the person cannot recognise the distinct parts of their own body.

Diagnosis And Treatment

The healthcare provider initially conducts a series of examinations posed to the patient, to verify that no sensory organ has suffered complete damage or loss of function. These comprise copying and matching quizzes, like grouping together pictures that belong in the same category, identifying foods that resemble one another in taste or smell, comparing noises that sound alike. Moreover, the patient’s fluency in speaking and level of intelligence are also gauges, to ensure there is no significant damage to the neural networks responsible for those operations.

Once the type and intensity of agnosia are determined in the patient, pertinent treatment options are given. Although there is no definitive cure yet for people who experience mild or severe circumstances of agnosia, remedial measures like speech therapy and occupational therapy can significantly improve the ability of sensory organs to operate smoothly. This aids the patient in performing routine tasks by themselves, by identifying and acknowledging the nerve signalling limitations, simplifying the methods of carrying out regular activities and augmenting assimilation of information by the brain.