Somatoparaphrenia is a type of
monothematic delusion
A monothematic delusion is a delusional state that concerns only one particular topic. This is contrasted by what is sometimes called ''multi-thematic'' or ''polythematic'' delusions where the person has a range of delusions (typically the case of ...
where one denies ownership of a limb or an entire side of one's body. Even if provided with undeniable proof that the limb belongs to and is attached to their own body, the patient produces elaborate
confabulations about whose limb it really is or how the limb ended up on their body.
In some cases, delusions become so elaborate that a limb may be treated and cared for as if it were a separate being.
Somatoparaphrenia differs from a similar disorder,
asomatognosia
Asomatognosia (also Somatoagnosia) is a neurological disorder characterized as loss of recognition or awareness of part of the body.Vallar, G. & Ronchi, R. (2009). Somatoparaphrenia: a body delusion. A review of the neuropsychological literature. ...
, which is characterized as loss of recognition of half of the body or a limb, possibly due to
paralysis
Paralysis (: paralyses; also known as plegia) is a loss of Motor skill, motor function in one or more Skeletal muscle, muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory d ...
or
unilateral neglect
Hemispatial neglect is a neuropsychological condition in which, after damage to one hemisphere of the brain (e.g. after a stroke), a deficit in attention and awareness towards the side of space opposite brain damage (contralesional space) is obse ...
.
For example, asomatognosic patients may mistake their arm for the doctor's. However, they can be shown their limb and this error is temporarily corrected.
Somatoparaphrenia has been reported to occur predominantly in the left arm of one's body, and it is often accompanied by left-sided paralysis and
anosognosia
Anosognosia is a condition in which a person with a disability is cognitively unaware of having it due to an underlying physical condition. Anosognosia results from physiological damage to brain structures, typically to the parietal lobe or a di ...
(denial or lack of awareness) of the paralysis. The link between somatoparaphrenia and paralysis has been documented in many clinical cases, and while the question arises as to whether paralysis is necessary for somatoparaphrenia to occur, it has been confirmed that anosognosia is not necessary, since cases of somatoparaphrenia and paralysis with no anosognosia have been documented.
History
Cases of somatoparaphrenia had been described since the end of the nineteenth century, but it wasn't until 1942 that
Gerstman introduced the term somatoparaphrenic symptoms, defined as illusions or distortions concerning the perception of the affected limb or side of the body, which is believed or experienced as absent. The term was coined from the Greek: παρά, ''para'' + φρεν, ''phren'', meaning "against the mind" and σώμα, ''soma'' (
stem
Stem or STEM most commonly refers to:
* Plant stem, a structural axis of a vascular plant
* Stem group
* Science, technology, engineering, and mathematics
Stem or STEM can also refer to:
Language and writing
* Word stem, part of a word respon ...
''somat–'') referring to the "body"; therefore, somatoparaphrenia is defined as a bodily delusion.
The main manifestation of somatoparaphrenia is the feeling of disownership of the contralesional body; the belief that contralesional body parts do not belong to them but to another person.
Reinstatement of ownership by third-person perspective does not permanently abolish somatoparaphrenia suggesting that the subjective sense of body ownership remains dominated by an impaired first-person representation of the body that cannot be updated.
Causes
It has been suggested that damage to the posterior
cerebral
Cerebral may refer to:
* Of or relating to the brain
* Cerebrum, the largest and uppermost part of the brain
* Cerebral cortex, the outer layer of the cerebrum
* Retroflex consonant, also referred to as a cerebral consonant, a type of consonant so ...
regions (
temporoparietal junction
The temporoparietal junction (TPJ) is an area of the brain where the temporal and parietal lobes meet, at the posterior end of the lateral sulcus (Sylvian fissure). The TPJ incorporates information from the thalamus and the limbic system as well ...
) of the
cortex
Cortex or cortical may refer to:
Biology
* Cortex (anatomy), the outermost layer of an organ
** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain''
*** Motor cortex, the regions of the cerebral cortex i ...
may play a significant role in the development of somatoparaphrenia. However, more recent studies have shown that damage to deep cortical regions such as the posterior insula and subcortical structures such as the
basal ganglia
The basal ganglia (BG) or basal nuclei are a group of subcortical Nucleus (neuroanatomy), nuclei found in the brains of vertebrates. In humans and other primates, differences exist, primarily in the division of the globus pallidus into externa ...
, the thalamus and the white matter connecting the thalamus to the cortex may also play a significant role in the development of somatoparaphrenia.
It has also been suggested that involvement of deep cortical and subcortical grey structures of the temporal lobe may contribute to reduce the sense of familiarity experienced by somatoparaphrenic patients for their paralyzed limb.
Treatment
One form of treatment that has produced a more integrated body awareness is
mirror therapy
Mirror therapy (MT) or mirror visual feedback (MVF) is a therapy for pain or disability that affects one side of the patient more than the other side. It was invented by Vilayanur S. Ramachandran to treat post-amputation patients who had phantom ...
, in which the individual who denies that the affected limb belongs to their body looks into a mirror at the limb. Patients looking into the mirror state that the limb does belong to them; however body ownership of the limb does not remain after the mirror is taken away.
See also
*
Allochiria
*
Body integrity dysphoria
Body integrity dysphoria (BID), also referred to as body integrity identity disorder (BIID), amputee identity disorder or xenomelia, and formerly called apotemnophilia, is a rare mental disorder characterized by a desire to have a sensory or ...
*
Body schema
Body schema is an organism's internal model of its own body, including the position of its limbs. The neurologist Henry Head, Sir Henry Head originally defined it as a postural model of the body that actively organizes and modifies 'the impressions ...
*
Cotard delusion
Cotard's syndrome, also known as Cotard's delusion or walking corpse syndrome, is a rare mental disorder in which the affected person holds the delusional belief that they are deceased, do not exist, are putrefying, or have lost their blood or ...
*
Phantom limb
A phantom limb is the sensation that an amputated or missing limb is still attached. It is a chronic condition that is often resistant to treatment. When the cut ends of sensory fibres are stimulated during thigh movements, the patient feels as ...
References
{{Delusion
Delusional disorders
Psychosis
Delusions