Case Vignettes in Neurology

PATIENT CASE STUDIES

Case 5 1/19 Disorders of sensation
Case discussion This 39-year old male, farmer, complained of symmetric tingling, numbness and weakness in his hands and feet. About 21/2 months previously he had developed "shingles" on his right shoulder and neck. Six week previously the tingling and numbness began in the toes and forefeet and distal lower legs and over a two week period progressed to above his knees and to fingers. He also complained of anorexia and a 10-pound weight loss. Mental status and cranial nerve examination were normal. Motor examination revealed 5/5 strength throughout except for mild 5-/5 weakness in distal lower extremities manifested with mild difficulty in standing on heels. DTRS were 1+ throughout, slightly decreased. Specifically, ankle reflexes were present and plantar reflexes were flexor. His gait was ataxic but finger to nose and alternating rapid movement tests were normal. Sensory examination revealed decreased sensation to pinprick over distal lower extremities and finger tips. Vibration sense and position sense were intact. General physical examination revealed transverse white lines on the finger nails and scars in the skin corresponding to the C4 dermatome on the right.
Summarize the Case in 1-2 sentences. This is a 39-y/o farmer with and 2-month progressive course of sensory changes and weakness in hands and feet associated with generalized hyporeflexia, ataxic gait, but intact vibration and position sense. Also complains of 10-lb weight loss in same time frame as well as a shingles-like skin erutption 2.5 months previously. good, on the long side Discuss lesion localization on the basis of the physical examination. peripheral nerve: bilateral sensory loss more prominent than weakness, pinprick affected more than vibration and position sense. good Discuss underlying pathogenesis on the basis of clinical course. subacute course implies inflammatory, toxic/metabolic, neoplastic, or infectious process. good Indicate one likely clinical diagnosis. List (or classify) alternative diagnoses. mixed sensorimotor polyneuropathy due to chronic arsenic poisoning--Mees lines on fingernails, anorexia, exposure to pesticides (farmer) good metabolic disorders: nutritional deficiencies (B12, folate, thiamine), diabetes, chronic liver disease, uremia á toxic--heavy metals (lead), alcoholism, drugs--INH, cytotoxics, ddC, metronidazole. á chronic disease: AIDS, multiple myeloma, connective-tissue diseases (SLE, RA, PN, sarcoid) á other: neurosyphilis/abes dorsalis, good Indicate 2 ancillary tests that would assist in confirming or refuting the clinical diagnosis. Indicate the test results that would confirm the clinical diagnosis. nerve conduction studies-- decreased amplitude of evoked potentials, and slowed conduction increased hair and urine arsenic levels--but urine levels may be affected by some foods (e.g. seafood) this is an axonal neuropathy; you tend to see decreased amplitude of evoked responses but not much slowed conduction. why? Indicate complications of the disease and ancillary tests that would help evaluate them. Encephalopathy may develop, manifested by headache, altered mental state, and convulsive seizures. Hemolytic anemia may also develop, and can be monitored with periodic CBC. (Adams 1212) good Discuss how the underlying pathophysiology is relevant in the management of this patient. Arsenic's toxicity is related to its covalent bonding with sulfhydryl groups of enzymes needed for cellular metabolism, especially pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, which halts respiration. (Voet & Voet, 513). Nerves are particularly sensitive to reduced energy production, and thus neurologic symptoms are prominent in chronic poisoning. good, they bind lipoic acid a cofactor to one of the catalytic components of pyruvate dehyrogenase. Chelation with dimercaprol (BAL) IM for 2 days, followed by oral penicillamine to remove excess arsenic, usually leads to gradual resolution of the polyneuropathy (Adams, 1212). (Interestingly, arsenic compounds were used as an early treatment of syphilis, because microbial enzymes seem even more sensitive to As than mammalian enzymes) Sources: Adams, Victor, Ropper, Principles of Neurology, 6th Ed. 1997. Voet and Voet, Biochemistry, 1990 good

Case 5 1/19 Disorders of sensation

Case discussion

This 39-year old male, farmer, complained of symmetric tingling, numbness and weakness in his hands and feet. About 21/2 months previously he had developed "shingles" on his right shoulder and neck. Six week previously the tingling and numbness began in the toes and forefeet and distal lower legs and over a two week period progressed to above his knees and to fingers. He also complained of anorexia and a 10-pound weight loss.

Mental status and cranial nerve examination were normal. Motor examination revealed 5/5 strength throughout except for mild 5-/5 weakness in distal lower extremities manifested with mild difficulty in standing on heels. DTRS were 1+ throughout, slightly decreased. Specifically, ankle reflexes were present and plantar reflexes were flexor. His gait was ataxic but finger to nose and alternating rapid movement tests were normal. Sensory examination revealed decreased sensation to pinprick over distal lower extremities and finger tips. Vibration sense and position sense were intact. General physical examination revealed transverse white lines on the finger nails and scars in the skin corresponding to the C4 dermatome on the right.

Summarize the Case in 1-2 sentences.

This is a 39-y/o farmer with and 2-month progressive course of sensory changes and weakness in hands and feet associated with generalized hyporeflexia, ataxic gait, but intact vibration and position sense. Also complains of 10-lb weight loss in same time frame as well as a shingles-like skin erutption 2.5 months previously.

good, on the long side

Discuss lesion localization on the basis of the physical examination.

peripheral nerve: bilateral sensory loss more prominent than weakness, pinprick affected more than vibration and position sense.

good

Discuss underlying pathogenesis on the basis of clinical course.

subacute course implies inflammatory, toxic/metabolic, neoplastic, or infectious process.

good

Indicate one likely clinical diagnosis. List (or classify) alternative diagnoses.

mixed sensorimotor polyneuropathy due to chronic arsenic poisoning--Mees lines on fingernails, anorexia, exposure to pesticides (farmer)

good

metabolic disorders: nutritional deficiencies (B12, folate, thiamine), diabetes, chronic liver disease, uremia

á toxic--heavy metals (lead), alcoholism, drugs--INH, cytotoxics, ddC, metronidazole.

á chronic disease: AIDS, multiple myeloma, connective-tissue diseases (SLE, RA, PN, sarcoid)

á other: neurosyphilis/abes dorsalis,

good

Indicate 2 ancillary tests that would assist in confirming or refuting the clinical diagnosis. Indicate the test results that would confirm the clinical diagnosis.

nerve conduction studies-- decreased amplitude of evoked potentials, and slowed conduction

increased hair and urine arsenic levels--but urine levels may be affected by some foods (e.g. seafood)

this is an axonal neuropathy; you tend to see decreased amplitude of evoked responses but not much slowed conduction. why?

Indicate complications of the disease and ancillary tests that would help evaluate them.

Encephalopathy may develop, manifested by headache, altered mental state, and convulsive seizures. Hemolytic anemia may also develop, and can be monitored with periodic CBC. (Adams 1212)

good

Discuss how the underlying pathophysiology is relevant in the management of this patient.

Arsenic's toxicity is related to its covalent bonding with sulfhydryl groups of enzymes needed for cellular metabolism, especially pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, which halts respiration. (Voet & Voet, 513). Nerves are particularly sensitive to reduced energy production, and thus neurologic symptoms are prominent in chronic poisoning.

good, they bind lipoic acid a cofactor to one of the catalytic components of pyruvate dehyrogenase.

Chelation with dimercaprol (BAL) IM for 2 days, followed by oral penicillamine to remove excess arsenic, usually leads to gradual resolution of the polyneuropathy (Adams, 1212).

(Interestingly, arsenic compounds were used as an early treatment of syphilis, because microbial enzymes seem even more sensitive to As than mammalian enzymes)

Sources: Adams, Victor, Ropper, Principles of Neurology, 6th Ed. 1997. Voet and Voet, Biochemistry, 1990

good