Neuropathies in the Older Patient - Essay Example

?Neuropathies in the older patient Peripheral neuropathy is a term used to describe disorders of the peripheral nervous system. The disorders have animpact on the axon and/or myelin sheath1, whose key function is increasing the speed of transmission of nerve impulses. According to Gray’s Anatomy, the peripheral nervous system is made up of a series of nerves connecting the central nervous system that is, the brain and the spinal cord to various tissues e.g., muscles and skin, and internal organs. The peripheral nerves consist of the motor, sensory and autonomic nerves, each peripheral nerve performing a specific function. Hence, any injury to or disease of the peripheral nervous system could result in demyelination or axonal degeneration leading to disruption of the sensory and/or motor function of the affected nerve2. Peripheral neuropathy manifests most commonly as numbness, tingling and pain in feet and hands due to nerve damage. More severe symptoms include burning pain, muscle wasting, anomalies in organ and gland function, and paralysis2. Difficulty in food digestion, erratic maintenance of blood pressure levels, abnormal sweating and sexual dysfunction are other symptoms of peripheral neuropathy2. This objective of this paper is to discuss in detail the types of peripheral neuropathy observed in the older patients, their causes and diagnoses. Peripheral neurologic deficits especially losses of vibratory sensation and ankle reflexes are frequently observed in older patients during physical examination3. Epidemiologists believe that nearly 8% of people above 60 years of age are likely to have peripheral neuropathy4. Moreover, the incidence of peripheral neuropathy increases with advancing age1. Sensory changes including visual impairment, changes in hearing, smell, taste and peripheral sensation may be related to the aging process itself 3,1. Besides, in patients of advanced age, increased incidence of chronic systemic diseases triggering neuropathy, and the use of medications causing neurotoxic effects are also factors leading to the development of peripheral neuropathy1. The frequency of age-related neuropathy is constantly rising in the developed world as a result of improved longevity among the people1. According to Rajabally1, peripheral neuropathy in more than 50% of the elderly is caused by impaired glucose metabolism. So also, with increasing age, cases of cryptogenic neuropathy, that is, neuropathy with no clearly identifiable cause are more common1. Over-weight persons are prone to have diabetes and are, therefore, more likely to have neuropathy3. In the absence of any systemic diseases in the older patients, and when symptoms are relatively minor and mostly non-disabling, there is a tendency among caregivers to give less attention than required to neuropathy. However, studies have found strong evidence of a link between peripheral neuropathy and functional disability including impaired balance resulting in falls, deformities of the joints, leg cramps and muscular weakness1. Symptomatic manifestations and diagnosis of peripheral neuropathy in the older patients Idiopathic or age-related sensory neuropathy is often asymptomatic. Some changes in peripheral nerve function are increasingly observed clinically in older adults who show no overt symptoms. Achilles areflexia was observed in 25% of the subjects over the age of 60 who were part of a large meta-analysis while more than 33% of the subjects had reduced vibration sense at the big toes and absent ankle reflexes5. Clinical manifestations of neuropathic symptoms are highly variable and depend on the type and cause of neuropathy. Hence, taking an extensive patient history is required. According to NINDS Fact Sheet2, when damage to only one nerve is involved, it is known as mononeuropathy. When multiple nerves are damaged and affect all limbs, it is referred to as polyneuropathy. Involvement of two or more nerves in different parts of the body are involved, known as mono-neuritis multiplex, it may cause deep pain. The very frequently reported symptoms of peripheral neuropathy are those of paresthesia (i.e., an abnormal sensation of tingling or pricking) and dysesthesia (i.e., an abnormal sensation of numbness, burning or pain) in the distal extremeties1,2. These symptoms are caused due to small sensory fiber damage. When the large sensory fibers are damaged, imbalance and rarely sensory ataxia are experienced. Motor nerve damage causes muscular weakness and excruciating cramps2 while muscle loss and fasciculations (involuntary muscle twitching visible under the skin) are noted especially when the disease has progressed for long1. Bone degeneration also occurs due to motor nerve damage2. Damage to autonomic fibers leads to orthostatic hypotension, abnormal sweating, sexual dysfunction and abnormal bowel and bladder performance1,2. Diagnosis of neuropathy related to large-sensory fibers is possible through neurological evaluation. The presence of neuropathy is established by testing the response to light touch, pin prick, heat and cold, and vibration. Pain and temperature sensations are transmitted by the small sensory fibers. Hence, damage to these fibers can manifest as an inability to perceive pain or heat. In contrast to this, oversensitization of the pain receptors in the skin can occur leading to allodynia or perception of severe pain from painless stimuli2. Although the ability to perceive painful stimuli is preserved with progressing age, the reaction time for retreating from such stimuli may become slow with age6. In radiculoneuropathies e.g., Guillaine-Barre syndrome (GBS), a predominant proximal weakness is observed1. Autonomic nerve dysfunction can cause severe breathing impairment or irregular heart beat and lead to life threatening situations2. Cardiovascular autonomic neuropathy manifests as orthostatic hypotension, irregular heart beats and reduced heart rate variability7. Autonomic neuropathy could also cause gastrointestinal symptoms. As a result of damage to autonomic nerves the intestinal muscle contractions are affected leading to diarrhea, constipation, or incontinence2. Routine blood investigations are to be compulsorily done before evaluating neuropathy in elderly patients. Given the high incidence of neuropathy due to impaired glucose metabolism in the elderly, a glucose tolerance test is imperative. Paraneoplastic neuropathies are frequently observed in the higher age group patients. Hence, testing for antineuronal antibodies is recommended1. Additionally, CT scanning of the thoracic, abdominal and pelvic regions is also recommended to be done. Also, according to Rajabally1, an X-ray of the chest is especially required for all newly diagnosed patients. Electrophysiological examination besides enabling firm diagnosis of a large-fiber neuropathy, will also be helpful in the classification of the diagnosis as purely sensory, sensorimotor, or purely motor neuropathy subtype1. It also provides crucial information on the neuropathy vis a vis whether it is axonal or demyelinating. To diagnose the exact cause of neuropathy, additional investigations such as CSF examination are undertaken. Nerve biopsy is done to especially to investigate painful cryptogenic neuropathy. Causes of peripheral neuropathy in the older people The most commonly determined causes of peripheral neuropathy in the aged westerners are acute neuropathies such as acute inflammatory demyelinating polyradiculoneuropathy (e.g., GBS) and vasculitic neuropathy. The chronic neuropathies identified in the older patients include neuropathy due to impaired glucose metabolism (or diabetic neuropathy), chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), and neuropathy due to nutritional and vitamin deficiency. Neuropathies due to dysfunction of various organs including neuropathy due to liver disease, renal-induced neuropathy, COPD-related polyneuropathy, hypothyroid neuropathy are known1. Besides, a number of drugs used by the older patients can cause neuropathies. One example is almitrine, the drug used to treat COPD is linked to a distal sensory axonopathy. Treatment of age-related neuropathies Nerve conduction studies indicate that nearly 50% of diabetics have asymptomatic neuropathy. The treatment of diabetic neuropathy is mainly based on symptoms with medication to treat neuropathic pain being the most utilized. Tricyclic antidepressants have also been found useful in the treatment of neuropathy due to diabetes1. Steroids, intravenous immunoglobulins and plasma exchanges are the mode of treatment of CIDP. Nutritional and vitamin deficiency related neuropathies are not common in the developed countries. This type of neuropathy is curable1. Deficiencies in the older people are caused due to poor dietary habits, alcoholism and poor absorption on account of gastrointestinal problems. Deficiency of the vitamin B group in particular B1 (thiamine), B6 (pyridoxine), B12 (cobalamin), and folate are generally involved. In conclusion peripheral neuropathy is a common but often neglected disorder in the older patients. Symptomatic neuropathies are identifiable through detailed case history and neurological examination. Treatment protocols are available for the various neuropathies which, though unable to reverse the condition, can definitely improve the quality of life for the elderly patients. References 1. Rajabally YA, 2006. Neuropathies in the older patient. Reviews in Clinical Gerontology 16:113-124. 2. National Institute of Neurological Disorders and Stroke, 2011. Peripheral neuropathy fact sheet. NIH Publication No. 04-4853. Accessed 1 October 2011 from http://www.ninds.nih.gov/disorders/peripheralneuropathy/detail_ peripheralneuropathy.htm 3. Mold JW, Vesely SK, Keyl BA et al., 2004. The prevalence, predictors, and consequences of peripheral sensory neuropathy in older patients. The Journal of the American Board of Family Practice 17:309-318. 4. Martyn CN, Hughes RA. 1997. Epidemiology of peripheral neuropathy. J Neurol Neurosurg Psychiatry 52:310-318. 5. Vranken AF, Kalmijn S, Brugman F, et al., 2006. The meaning of distal sensory loss and absent ankle reflexes in relation to age. A meta-analysis. J Neurol., 253: 578- 589. 6. Cacchione PZ, 2005. Sensory changes. Hartford Institute for Geriatric Nursing. Accessed on 2 October 2011 from http://consultgerirn.org/topics/sensory_changes/want_to_know_more 7. Moran A, Palmas W, Field L et al., 2004. Cardiovascular autonomic neuropathy is associated with microalbuminuria in older patients with type 2 diabetes. Diabetes Care 27 (4): 972-977. Read More