Unit 8. Case Study 1. Sannu’s Story Sannu has contracted Leprosy. As a sixteen year old teenager, it is hard to pin point when he was infected since Leprosy has a long incubation period. As a small boy traveling barefoot along trails in his village, Sannu’s body has already adapted to his living conditions. Sannu’s feet are tough and calloused. As Sannu ages, so does his Leprosy infection progress. The infection will cause neuropathy in his extremities which will lead to many injuries to his feet and hands. The wounds acquired will be infected for weeks or even months without treatment.
The neuropathy caused by the Leprosy infection is characterized by causing a decrease in sensation in the extremities, muscle weakness, and numbness. Sannu’s feet that have been toughened by his environment and life style have been further injured due to lack of sensation and medical treatment. In an attempt to keep his feet clean to aide the healing of his infections, Sannu is more than likely maintaining a sedentary life style. This life style along with the progression of the Leprosy infection will weaken Sannu’s muscles. A feature common to all forms of Leprosy is nerve infection.
Nerve damage appears to result from the multiplication of bacilli within Schwann cells and damage to the perineurium. Most of the deformities occurring from Leprosy are in fact due to trauma or a secondary infection. In a Leprosy infection one of the first symptoms are anesthesia to heat and cold. Leprosy affects the peripheral nervous system by attacking the myelin sheath surrounding the axons which affects the reliability and speed of nerve impulses. In other words, the nerve fibers are no longer insulated and nerve impulses cannot be conducted efficiently.
There are different types of sensory receptors located throughout the body and are designed based on a selective stimulus response. The appropriate receptive field is stimulated within a sensory receptor producing a response. In Sannu’s condition this action is delayed or absent due to the damage of his free nerve endings. Free nerve endings detect pain, temperature, and touch as well as tickle and itch. Sannu’s encapsulated nerve endings are also damaged. Encapsulated nerve endings detect pressure, vibration, and touch sensations.
When Dianna performed the tests to check Sannu’s Achilles tendon and Babinski’s reflex, she was evaluating his somatic senses. Somatic senses involve sensations such as touch, pressure, and pain as well as temperature perception. These are all affected in Leprosy infection. In Sannu’s case he has also lost the sensations of touch, pressure, and pain in his feet and hands due to the affects of leprosy on his nociceptors, mechanoreceptors, proprioceptors, and exteroceptors. These sensations are also present in the sensory receptors free nerve endings and encapsulated nerve endings.
Sannu’s interoceptors would not be affected in a Leprosy infection because interoceptors pertain to the body’s internal environment. Mycobacterium leprae grow best in relatively cool areas of the body such as: the skin, peripheral nerves, the mucosa of the upper respiratory tract as well as the chamber of the eye and in severe untreated cases the testes and eventually other vital organs. Leprosy affects the exteroceptors of the external surface of the body. Nociceptors are the receptors of pain and are located in all tissues of the body with an exception of the brain.
Proprioceptors do no adapt very much, this is why Sannu still feels pain in his leg that has been amputated. Sannu’s pain is slow pain. Slow pain is referring to pain that is chronic, burning, aching, or throbbing. The peripheral receptors activated during a stimulus are the nociceptors. Like other cutaneous and subcutaneous receptors, Nociceptors transduce a variety of stimuli into receptor potentials. Also, like other somatic sensory receptors, Nociceptors arise from cell bodies in dorsal root ganglia that send one axonal process to the periphery and the other into the spinal cord or brain stem.
Peripheral Nociceptors terminate at the site of free nerve endings. Nociceptors are located in the entire body except for the brain. The loss of myelination causes impulses to misfire. Without the myelin sheath the impulses are slower and misdirected. Sannu had little sensation to his extremities because of the process related to his Leprosy infection. Phantom limb pain is a result of neuroplasticity (new neural links can be made), or the brain region that once was responsible for controlling the amputated limb is taken over by an adjacent area of the brain.
The phantom limb pain is enhanced by referred sensations, so that stimuli applied to other body parts can be sensed from the phantom limb. In patients with Leprosy, phantom limb pain will not occur with only the amputation of fingers, toes, hands, or feet. Phantom limbs and phantom limb pain will only occur when the amputation is taken up to the stump of that limb. The representation of Sannu’s amputated leg on the somatosensory map will involve referred sensations because of remapping of somatosensory areas in the brain. The activity of the somatosensory map in the brain leads to conscious experience of body image and somatic sensations.
After Sannu’s amputation it is possible for him to initially experience some effects on his balance and equilibrium. This is because after amputation Sannu may still have confused senses of his missing leg. With the introduction of a prosthesis, Sannu’s brain will connect to the prosthetic device causing his brain to remember how to function as if the original leg were still there. The initial sensory loss that Sannu experienced was due to interference of the sensory pathway transmission. Leprosy affects the skin and peripheral nerves which are closest to the exterior of the body where the sensory receptors are located.
Leprosy infection is caused by mycobacterium leprae and mycobacterium lepromatosis. Both forms affect the peripheral nervous system by attacking the Schwann cells, destroying the myelin. At the site of the Schwann cell, the bacteria multiply and cause damage of the nerve architecture and cause secondary inflammation. This disease process results in desensitizing sensory receptors. This is why when Sannu cut his foot, he did not feel the pain, nor the infection that followed. Due to his location in a remote village and lack of medical care, his infection resulted in an amputation.
The receptors that should have sensed the initial injury to Sannu’s foot are the exteroceptors. Exteroceptors are responsible for responding to stimulus from outside the body such as touch, pressure, pain, and temperature. After Sannu’s amputation he began experiencing phantom limb sensations. This is considered as a form of neuropathic pain. It is presumed to be a response by the peripheral nervous system and the central nervous system of an injury. The process of reorganizing occurs from retained nerves from the amputated limb, spinal cord, thalamus, and cerebral cortex.
After an amputation the area of the brain that is responsible for processing the sensations from the missing limb are taken over by areas that neighbored the missing limb. It is believed that around 95% of people are naturally immune to Leprosy. Recent research suggests that there is a defect in cell-mediated immunity that causes susceptibility to Leprosy. The area of DNA responsible for that variable is also found in Parkinson’s disease. It is speculated the two disorders are linked somehow at the biochemical level. Research has shown that susceptibility to the disease was linked to region q25 on the long arm of chromosome 6.
Further study indicated that the Leprosy susceptibility gene lies within a region shared by two genes for Parkinson’s disease. Resources The Merk Manual of Diagnosis and Therapy “Infectious Diseases caused by Mycobacteria” 2004 International Journal of Leprosy and other Mycobacterial Diseases “Linkage of Leprosy Susceptibility to Parkinson’s Disease Genes” June 2004 www. who. ch/program infolep@antenna. nl www. encyclopedia. com www. ncbi. nlm. nih. gov/pubmed/15372437 en. wikipedia. org/wiki/proprioception rarediseases. about. com. lepercolonies. thalidomide May 16 2009 pubmed. gov Muscle Nerve October 30 2004