Agraphesthesia is a
disorder
Disorder may refer to randomness, non-order, or no intelligible pattern.
Disorder may also refer to:
Healthcare
* Disorder (medicine), a functional abnormality or disturbance
* Mental disorder or psychological disorder, a psychological pattern a ...
of directional cutaneous
kinesthesia
Proprioception ( ), also referred to as kinaesthesia (or kinesthesia), is the sense of self-movement, force, and body position. It is sometimes described as the "sixth sense".
Proprioception is mediated by proprioceptors, mechanosensory neurons ...
or a
disorientation
Orientation is a function of the mind involving awareness of three dimensions: time, Location (geography), place and person. Problems with orientation lead to ''dis''orientation, and can be due to various conditions, from delirium to Substance int ...
of the skin's sensation across its space. It is a difficulty recognizing a written
number
A number is a mathematical object used to count, measure, and label. The original examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can be represented in language with number words. More universally, individual numbers c ...
or
letter
Letter, letters, or literature may refer to:
Characters typeface
* Letter (alphabet), a character representing one or more of the sounds used in speech; any of the symbols of an alphabet.
* Letterform, the graphic form of a letter of the alphabe ...
traced on the skin after
parietal damage.
Causes
Agraphesthesia, or the lack of
graphesthesia ability, results from brain damage, particularly to the parietal lobe,
thalamus
The thalamus (from Greek θάλαμος, "chamber") is a large mass of gray matter located in the dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the thalamus to the cerebral cortex in all directions, ...
, and
secondary somatosensory cortex
The human secondary somatosensory cortex (S2, SII) is a region of cortex in the parietal operculum on the ceiling of the lateral sulcus.
Region S2 was first described by Adrian in 1940, who found that feeling in cats' feet was not only represente ...
.
A significant relationship has been found between agraphesthesia and people living with
Alzheimer's disease
Alzheimer's disease (AD) is a neurodegeneration, neurodegenerative disease that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in short-term me ...
. Alzheimer's patients typically experience the lack of sensation in both their dominant and non-dominant hands.
[Davis 2010, p. 264.] Astereognosis
Astereognosis (or tactile agnosia if only one hand is affected) is the inability to identify an object by active touch of the hands without other sensory input, such as visual or sensory information. An individual with astereognosis is unable to i ...
, the inability to identify a physical object solely by touch, is commonly found in conjunction with agraphesthesia in Alzheimer's patients.
[Davis 2010, p. 265.] Some research suggest that agraphesthesia can be used to track the cognitive decline in Alzheimer's patients once the disease is diagnosed.
Studies also show that patients diagnosed with
schizophrenia
Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social withdra ...
and their immediate relatives have a decreased ability to perform graphesthesia tasks in comparison to people without relatives diagnosed with schizophrenia. Therefore, researchers have suggested that somatosensory dysfunction in the parietal cortex is a potential cause of graphesthesia impairments.
Diagnosis
A diagnosis of agraphesthesia is determined using a variety of tests, such as the Palm Writing subtest. The Palm Writing subtest involves a series of trials where patients are asked to identify whether an X or an O was written on the palm of their hand.
Just as numbers and shapes may be used in addition to letters, similar neurological tests can be carried out on other parts of the body, such as the forearm and the abdomen. For tests of graphesthesia like the Palm Writing subtest, it is important that subjects do not see what is being traced on their palm because this can bias the subjects' responses.
[Chang 2004, p. 330.] Subjects can be blindfolded or a screen can be used to obstruct the subject's view of the area being tested.
Notes
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References
*Chang, Bernard P. and Mark F. Lenzenweger (2004). "Investigating Graphesthesia Task Performance in the Biological Relatives of Schizophrenic Patients", ''Schizophrenia Bulletin'', 30(2).
*Davis, Andrew S., Anna Mazur-Mosiewicz, and Raymond S. Dean (2010). "The Presence and Predictive Value of Astereognosis and Agraphesthesia in Patients with Alzheimer's Disease", ''Applied Neurophsychology'', 17. DOI: 10.1080/09084282.2010.525102
*Morch, Carsten Dahl, Ole K. Andersen, Alexandre S. Quevedo, Lars Arendt-Nielsen, and Robert C. Coghill (2010). "Exteroceptive Aspects of Nociception: Insights from Graphesthesia and Two-Point Discrimination", ''Pain'', 151(1).
Proprioception