Have you ever tried to visualize your hands… after closing your eyes? Previous studies had shown that we tend to underestimate our finger length increasingly from thumb to little finger. Researchers at Birkbeck, University of London,  made a new discovery after examing a 38-year-old woman born without a left arm. Your brains do not require visual or sensory input to represent your hands!

New Scientist reports:

For the first time, the perceived shape of a phantom limb has been measured. This should make it possible to learn more about how the brain represents what we look like.

The illusion of a phantom limb can kick in after an amputation or in people missing limbs from congenital disease. The result is the sensation that the limb is, in fact, present.

One theory suggests people with phantom limbs take cues from those around them to work out what their missing body part looks like. Another theory is that the sensation of an invisible limb reflects brain activity in regions that map our body in space.

To clarify the sensory origins of phantom limbs, Matthew Longo at Birkbeck, University of London, and colleagues enlisted the help of CL – a 38-year-old woman born without a left arm, who periodically feels she has a phantom hand. They asked her to place her right hand beneath a board and indicate where she believed her fingertips and knuckles were. She then repeated the exercise imagining that her phantom left hand was beneath the board instead.

Previous studies have shown that we tend to underestimate our finger length increasingly from thumb to little finger. This mirrors differences in the sensitivity and size of areas in the brain’s  somatosensory cortex that are thought to represent each digit, probably by making use of visual, mechanical and tactile feedback. The thumb is represented by a larger area of the cortex than the little finger.

As expected, CL reported these characteristic distortions when indicating the dimensions of her right hand. But she made the same errors when describing her phantom hand, implying she perceives both hands in the same way (Clinical Psychological Science).

That suggests there is “some structural representation in the brain of a body part that has never existed”, says Patrick Haggard at University College London, another member of the team. This implies that the somatosensory cortex does not require visual or sensory input to represent a body structure.

Understanding how the brain perceives the body could have broader implications. Longo says there are a few studies showing that people with eating disorders may inaccurately judge the size of their body from tactile feedback. Those results suggest there may be some relation between somatosensory representations of the body and our conscious feelings of what our body is like,” he says.

Read more about previous research that demonstrated through hand projections how faulty body perceptions work in  anorexia and other eating discorders:

Hand projections demonstrate how anorexia works 


A 48-year-old man presents with a 10-day history of fever, hand pain, watery diarrhea, weight loss, anorexia, and intermittent vomiting. Two nodules are noted on both thumbs of his hands. What is the diagnosis?

Medscape Case:

The lesions depicted in the photographs are Osler’s nodes. The nodes coupled with the clinical history were suspicious for infective endocarditis (IE). Medical records were obtained while the patient was undergoing evaluation in the ED. During his recent admission for these symptoms, he was told that he had endocardial vegetations and was treated with antibiotics, but he left the hospital against medical advice. Given his recent evaluation, subjective fevers, and the physical finding of Osler’s nodes, he was admitted for treatment of IE.

The incidence of IE ranges from 2.4 to 11.9 cases per 100,000 patient years. Of these, half occur in patients between the ages of 31 to 60 years. It is much more common in patients with preexisting cardiac structural anomalies or with other risk factors, such as injection drug use, prosthetic cardiac valves, or indwelling intravenous catheters. Native-valve IE occurs in 59% to 70% of cases, whereas prosthetic valve IE occurs in 14% to 30% of the time. Infective endocarditis associated with injection drug use accounts for 11% to 16% of cases.

The clinical presentation of infective endocarditis may vary. Patients whose IE is caused by highly virulent organisms, such as S aureus, have much higher morbidity and mortality, and they typically present with high fevers and rapid cardiopulmonary collapse. This rapidly deteriorating clinical course culminating in death within a few days is often referred to as acute bacterial endocarditis. Subacute bacterial endocarditis is a more indolent disease caused by less virulent bacteria, such as Streptococcus, and patients present with fever, malaise, and other nonspecific symptoms. The clinical presentation of IE can occur along a continuum between acute and subacute clinical pictures and may have overlapping bacterial etiologies. Classic presentations are uncommon; patients with IE can present with fever, chills, weakness, dyspnea, anorexia, malaise, nausea, and vomiting. In a busy ED, these common chief complaints can be easily overlooked.

Physical examination findings of IE include Osler’s nodes, Janeway lesions, Roth spots, and infectious embolic complications. Roth spots are not specific for IE and can occur in the context of other illnesses, such as systemic lupus erythematosus; however, Osler’s nodes and Janeway lesions are highly specific for IE. Osler’s nodes are small, painful nodules that appear on the palms of the hands and soles of the feet as well as the distal phalanges. They are between 2 mm and 15 mm in diameter, occasionally have a blanched center, are usually multiple, and transiently appear and resolve at different times over a period of days. There is disagreement about the etiology of these nodes. Many sources believe that Osler’s nodes are vascular phenomena resulting from immune-complex deposition into the vascular endothelium, whereas others describe the lesions as the result of microabscesses within the dermal arterioles and the papillary dermis. In contrast to painful Osler’s nodes, Janeway lesions are painless hemorrhagic plaques that are mostly present on the palms or soles. Roth spots are oval retinal hemorrhages located near the optic disc. Infectious valvular vegetations can embolize to the brain in up to 40% of IE cases; however, central nervous system manifestations of IE are not diagnostic of the condition.

The Duke Criteria used to diagnose endocarditis may be fulfilled by the finding of 2 major criteria, 1 major and 3 minor, or 5 minor criteria. The major criteria include 2 positive blood cultures or evidence of endocardial involvement on echocardiography. Minor criteria include predisposing factors, fever, vascular phenomena, immunologic phenomena, other microbiologic evidence (not meeting major criteria), and other echocardiographic findings (not meeting major criteria).

Given the diagnostic requirements, initial diagnostic studies include blood cultures, echocardiography, electrocardiography, and chest radiography. Blood cultures should be drawn from 3 separate sites over the course of an hour to increase the likelihood of identifying the bacterial species. Antibiotic therapy for acutely ill patients should be administered promptly. Cardiac echocardiography, either by noninvasive transthoracic echocardiography or transesophageal echocardiography (TEE, which is more sensitive and specific for diagnosing IE), can aid in the diagnosis of IE and provide critical information regarding the structure and function of the affected valves. Electrocardiographic findings are often nonspecific or normal, but they can show characteristic PR interval prolongation, bundle branch block, or complete heart block when the infection affects the conduction system. Surgical intervention is usually reserved for patients with severe valvular dysfunction, which is best elucidated by TEE; however, several other indications for surgery exist. Management of these patients requires infectious disease consultation.

The mainstay of treatment of bacterial endocarditis is intravenous antibiotics. Empiric therapy should be based on the characteristics of the given patient, whether an artificial valve is or is not involved, and local resistance patterns. Ultimately, definitive therapy should be based on the results of the blood culture and sensitivity. Empiric antibiotic therapy for endocarditis is tailored to cover the organisms that are most likely to infect a given patient group. For uncomplicated IE, bacteria commonly found in the upper respiratory tract, gastrointestinal tract, and skin are likely to be the causative bacterium in patients with native-valve endocarditis acquired in the community. These include staphylococci, viridans streptococci, and Streptococcus bovis, as well as the “HACEK” organisms (Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, and Kingella); therefore, for empiric therapy for uncomplicated native-valve IE, intravenous ceftriaxone or nafcillin plus gentamicin is recommended. If the incidence of methicillin-resistant S aureus (MRSA) is high, vancomycin should be used.

Complicated IE includes hospital-acquired infections, intravenous drug users, and artificial valve infections. Patients with hospital-acquired infections or intravenous drug use are more likely to have infection due to S aureus. Other common organisms for this patient population include gram-negative bacteria, such as Pseudomonas aeruginosa, group D enterococci, and fungal species (such as Candida). Patients with suspected MRSA infection, intravenous drug use, or suspected hospital-acquired infections should be empirically treated with a combination of vancomycin and gentamicin. For patients with artificial valves, the organisms are most likely to be S aureus and other coagulase-negative Staphylococcal species, enterococci, and gram-negative bacilli; therefore, these patients should be empirically treated with gentamicin, vancomycin, and rifampin. Rarely, patients with blood culture-negative endocarditis may be colonized with fastidious organisms, such as Granulicatella species, Abiotrophia species, Bartonella, Coxiella burnetii, Brucella, and Tropheryma whipplei.

Prophylaxis for patients with high-risk cardiac conditions (such as prosthetic heart valve or previous IE) is indicated when they are undergoing certain procedures. Amoxicillin or ampicillin is indicated for nonpenicillin-allergic patients 1 hour before the procedure. For penicillin-allergic patients, premedication with clarithromycin, azithromycin, clindamycin, cephalexin, cefazolin, or ceftriaxone is appropriate. Antibiotic or practice guideline references should be consulted before recommending prophylaxis.

The patient in this case was admitted and underwent TEE that confirmed the presence of 2 distinct lesions on the aortic valve suspicious for vegetations. He was started on a course of intravenous antibiotics, but unfortunately, he once again left the hospital against medical advice before completion of therapy.

FINAL HINT: Consider the history of fever, weakness, and tender, painful nodules on each thumb..

DIAGNOSIS: ‘Infectious endocarditis’  (in this case: resulting from injection drug abuse!).


Hand projections demonstrate how anorexia works

[tweetmeme source=”handresearch” only_single=false] Scientists at University College London asked people to put their left hands palm down under a board and judge the location of the covered hand’s knuckles and fingertips with a pointer. The results pointed out that people tend to think that their hands are wider and their fingers are shorter than they truly are. Lead researcher Dr Matthew Longo recognized how the findings may well be relevant to psychiatric conditions involving body image such as anorexia nervosa.

Susan Ringwood, chief executive of the eating disorders charity Beat, said:

“We know that one of the features of anorexia nervosa can be distorted body image. People affected can truly believe that they are grossly fat, even when they are dangerously underweight. They are able to judge other people’s bodies quite accurately and would describe someone else the same size as themselves correctly, but still not be able to do that about their own weight and shape.”

“This brain study may give some insight into how this could be possible, and could be very motivating for people with eating disorders to know that there was a biological explanation for their experiences, rather than feeling it was their fault.”

Obviously, the brain tends to make body image projections that are wider and shorter than the body (hand) really is. And women are typically known for experiencing more problems in visuo-spatial tasks!  

But there’s more known about how hands relate to anorexia… 



But there is another connection between anorexia nervosa and the hand:  it’s in the length of the fingers! 

High 2d:4d digit ratio (the typically female-like finger length variant) has been associated with low levels of prental testosterone exposure AND high levels of eating disordered behaviors. Michael D. Anestis reports:

“Drive for thinness was lower in men with a lower 2D:4D ratio and drive for muscularity was higher in men with a lower 2D:4D ratio. …A lower 2D:4D ratio also predicted lower levels of eating disordered behaviors in men. …So, what do these findings tell us?  First of all, it appears that, for men as with women, a greater level of prenatal testosterone is associated with less of a drive to be thin and lower levels of eating disordered behaviors.  Additionally, a greater level of prenatal testosterone exposure appears to predict a greater drive to develop a muscular physique.” 

So, next to the brain-created body image distortions – prenatal testosterone is also involved in anorexia nervosa related eating disorders.

Please feel free to share your thoughts…             


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