Damage done to these sensory fibers may lead to changes in sensation, a burning feeling, nerve pain, tingling, numbness, inability to determine joint position, and hypersensitivity to touch. These sensation changes often start in the feet and gradually spread to the other organ systems, depending on the degree of the neuropathy. In most metabolic and toxic disorders, it is the most distal part of the axons in nerves that deteriorates, with the breakdown of the myelin sheath.
Sensorimotor neuropathies are classified into different types, according to conditions that cause the neuropathy. Endocrine diseases include diabetes mellitus, hypothyroidism, and acromegaly. Nutritional diseases are alcoholism, vitamin B12 deficiency, folate deficiency, Whipple’s disease, postgastrectomy syndrome, gastric restriction surgery and thiamine deficiency. Hypophosphatemia, amyloidosis, gouty neuropathy, and sarcoidosis also exhibit symptoms pertaining to sensory nerve damage. Connective tissue diseases like rheumatoid arthritis, polyarteritis nodosa, systemic lupus erythematosus, Churg-Strauss vasculitis and cryoglobulinemia also have symptoms and complications affecting the sensorimotor nerves. AIDS and Lyme disease are types of infectious and inflammatory conditions that are part of what may cause sensory peripheral neuropathy. Excessive exposure to toxic substances, including heavy metals, leads to the development of a toxic neuropathy. Examples of these substances are acrylamide, carbon disulfide, dichlorophenoxyacetic acid, ethylene oxide, hexacarbons, carbon monoxide, organophosphorous esters, glue, arsenic, mercury, gold, and thallium.
Symptoms related to sensory nerve damage are comprised of a tingling feeling or paresthesia, hypesthesia or elevated sensitivity of affected areas, and numbness or diminished sensation. Multifocal neuropathies like mononeuritis multiplex that is brought about by polyarteritis nodosa causes sensory abnormalities in the nerve or root, with sensory loss in specific nerve distributions. Distal symmetric axonal neuropathy, a common diabetic complication, usually starts at the tips of the toes and progresses to adjacent organs in a stocking-and-glove distribution. Sensory examination of this neuropathy shows reduced sensitivity to light touch, pin prick response and temperature sensitivity in a stocking-and-glove distribution. Nerve pain is also seen due to repetitive stress from assembly line work or some sports like tennis and golf, wherein the median nerve and ulnar nerve are commonly affected.
Evaluation of sensory neuropathies include hematological and chemical blood tests such as fasting blood glucose, glycosylated hemoglobin levels, blood urea nitrogen, creatinine, complete blood cell count, and erythrocyte sedimentation rate. Tests such as urine analysis and the measurement of vitamin B12 and thyrotropin stimulating hormone levels are also suggested. A negative result in the initial blood tests does not signify a clean bill of health. It signifies that further neurologic tests should be made in order to make a full diagnosis and thus accurately treat the sensory peripheral neuropathy.