peripheral neuropathies

Question 1

Items 447–450
A 32-year-old man living along the coast of Massachusetts presents
with an acutely evolving left facial weakness. Although he has no facial
pain or numbness, he does complain of diffuse headache. He has no history
of diabetes mellitus or other systemic illnesses, but does report newly
appearing joint pains and a transient rash on his right leg that cleared spontaneously
more than 1 month prior to the appearance of the facial weakness.
On examination, he has mild neck stiffness and pain on hip flexion of
the extended leg.
447. This man is at highest risk for which of the following causes of a unilateral
facial weakness?
a. HIV-associated neuropathy
b. Lyme neuropathy
c. Diphtheritic polyneuropathy
d. Tuberculous meningitis
e. Schwannoma

Answer 1

447. The answer is b. (Victor, pp 768–770.) The clinical scenario presented
     is most consistent with a neuropathy of Lyme disease, the infection
     caused by Borrelia burgdorferi. This spirochetal infection is tick-borne and
     is endemic in the area where this patient lives. The rash on his leg was most
     likely erythema chronicum migrans, a target-shaped lesion that enlarges as
     the central area returns to normal. His complaints and examination suggest
     a chronic meningitis preceded by an arthralgia, a common neurologic scenario
     with Lyme disease. Facial weakness may be the only neurologic sign
     of Lyme disease. The neurologic deficits usually appear weeks after the initial
     rash. Untreated neurologic disease may persist for months. Optic neuritis
     may also appear in association with the chronic meningitis of Lyme
     disease. A schwannoma may develop on the seventh cranial nerve, but it
     would produce unilateral facial weakness followed by signs of brainstem
     compression. The cranial nerve dysfunctions associated with the early
     stages of diphtheritic polyneuropathy are a consequence of a toxin released
     by the infectious agent. Tuberculous meningitis may produce several different
     cranial nerve deficits. With HIV infection, a peripheral neuropathy
     may develop, but it typically affects the limb nerves, not the facial nerve.

Question 2

Items 447–450
A 32-year-old man living along the coast of Massachusetts presents
with an acutely evolving left facial weakness. Although he has no facial
pain or numbness, he does complain of diffuse headache. He has no history
of diabetes mellitus or other systemic illnesses, but does report newly
appearing joint pains and a transient rash on his right leg that cleared spontaneously
more than 1 month prior to the appearance of the facial weakness.
On examination, he has mild neck stiffness and pain on hip flexion of
the extended leg.

448. The physician concludes that the patient has tuberculous meningitis
     and treats him with isoniazid and rifampin. To avoid additional signs of
     neuropathy, which of the following agents should be administered along
     with these antibiotics?
     a. Ceftriaxone
     b. Thiamine
     c. Erythromycin
     d. Vitamin B12
     e. Pyridoxine

Answer 2

448. The answer is e. (Victor, p 1223.) These antituberculous drugs
     should be supplemented with pyridoxine to avoid a relative pyridoxine
     deficiency elicited by the isoniazid. The peripheral neuropathy evoked by
     the antituberculous agent will appear initially as disturbed sensation in the
     distal limbs. Paradoxically, pyridoxine overdose may also elicit a peripheral
     neuropathy, but overdose sufficient to produce a peripheral neuropathy is
     usually only seen in persons taking many times the recommended daily
     allowance of pyridoxine in vitamin preparations. It does not develop from
     eating foods with high levels of pyridoxine. Excessive pyridoxine consumption
     is usually linked to hypochondriasis or compulsive behavior.
     Ceftriaxone and erythromycin are appropriate antibiotics in the management
     of Lyme diseases. The cephalosporin is preferred unless the patient is
     intolerant of that class of antibiotics.
     305

Question 3

Items 447–450
A 32-year-old man living along the coast of Massachusetts presents
with an acutely evolving left facial weakness. Although he has no facial
pain or numbness, he does complain of diffuse headache. He has no history
of diabetes mellitus or other systemic illnesses, but does report newly
appearing joint pains and a transient rash on his right leg that cleared spontaneously
more than 1 month prior to the appearance of the facial weakness.
On examination, he has mild neck stiffness and pain on hip flexion of
the extended leg.

449. Because the facial weakness persists despite antituberculous treatment,
     the physician decides to administer high-dose steroids. Within 1
     week of the introduction of prednisone, the patient develops pain radiating
     down the back of his right leg and difficulty dorsiflexing the right foot. This
     new complaint probably represents which of the following disorders?
     a. Borrelia radiculopathy
     b. Diabetic mononeuritis multiplex
     c. Isoniazid neuropathy
     d. Rifampin toxicity
     e. Tuberculous radiculopathy

Answer 3

449. The answer is a. (Victor, pp 1393–1394.) This patient has, in effect,
     developed a noncompressive sciatica, or Lyme neuropathy. Dorsiflexion of
     the foot is controlled primarily by the anterior tibial muscle. The deep peroneal
     nerve supplies this muscle and arises from the common peroneal
     nerve just below the knee. A sciatic nerve injury may also produce footdrop,
     and irritation of spinal roots to the sciatic nerve produces the footdrop
     that may occur with Lyme radiculopathy. Lyme disease causes painful
     radiculopathies and peripheral neuropathies. Tuberculosis may cause similar
     complaints, but steroid therapy is often useful in suppressing that complaint
     in chronic tuberculous meningitis. Steroid-induced diabetes mellitus
     would be unlikely to evolve to the point that a painful neuropathy developed
     over so short a time.

Question 4

Items 447–450
A 32-year-old man living along the coast of Massachusetts presents
with an acutely evolving left facial weakness. Although he has no facial
pain or numbness, he does complain of diffuse headache. He has no history
of diabetes mellitus or other systemic illnesses, but does report newly
appearing joint pains and a transient rash on his right leg that cleared spontaneously
more than 1 month prior to the appearance of the facial weakness.
On examination, he has mild neck stiffness and pain on hip flexion of
the extended leg.

450. Eventually, the physician receives results of a diagnostic test and
     switches the patient to a cephalosporin. The man’s facial strength improves,
     but he notices twitching of the left corner of his mouth whenever he blinks
     his eye. This involuntary movement disorder is probably an indication of
     which of the following?
     a. Sarcoidosis
     b. Recurrent meningitis
     c. Aberrant nerve regeneration
     d. Mononeuritis multiplex
     e. Cranial nerve amyotrophic lateral sclerosis (ALS)

Answer 4

450. The answer is c. (Victor, p 287.) Aberrant regeneration of a cranial
     nerve is not all that uncommon, but it is more often seen after injury to the
     third nerve than to the seventh. For unknown reasons, the regenerating
     motor fibers miss their original targets and innervate new destinations.
     With cranial ALS, facial twitching occurs, but it is not preceded by unilateral
     weakness; and it is seen as the weakness evolves, not as it remits. Sarcoidosis
     may produce facial weakness with aberrant regeneration, but this
     patient’s history does not suggest this idiopathic granulomatous disease.
     There is nothing to suggest that his Lyme disease is recurring, although
     recurrent meningitis may develop with inadequate treatment

Question 5

451. A 25-year-old woman is being examined by her physician. The knee
     jerk is being tested. The patellar tendon reflex involves sensory fibers of the
     femoral nerve that originate in spinal segments
     a. S3–S4
     b. S2–S3
     c. S1–S2
     d. L4–L5
     e. L2–L3

Answer 5

.451. The answer is e. (Victor, p 49.) Myotactic, or tendon stretch, reflexes
require intact sensory supplies from the tendons and motor supplies to
the muscles involved. The patellar tendon reflex entails contraction of the
quadriceps femoris muscle group, a muscle group with four members:
the vastus lateralis, vastus medialis, vastus intermedius, and rectus femoris.
This reflex requires perception of stretch in the tendon stretch receptors
innervated by L2 and L3. With tapping of the tendon that extends from the
patella to the head of the tibia, spinal reflex pathways activate contraction of
the quadriceps femoris group and evoke extension of the lower leg with
straightening of the knee. Damage to the motor supply to the reactive
muscles must be profound before the tendon reflex will be lost completely.
Corticospinal tract damage will produce hyperreflexia, apparently by disinhibiting
spinal cord mechanisms.

Question 6

452. A 51-year-old factory worker has noticed progressive weakness over
     the past year. Examination and testing reveal a painless largely motor
     peripheral neuropathy. Of the following agents, the one most likely to be
     etiologic in this case is
     a. Lead
     b. Manganese
     c. Thallium
     d. Cyanide
     e. Mercury

Answer 6

452. The answer is a. (Victor, pp 1393–1394.) Lead poisoning, especially
     in adults, produces a painless neuropathy often targeting the radial nerve
     and resulting in a wristdrop. Lead poisoning in children is likely to produce
     increased intracranial pressure and cognitive dysfunction. Thallium
     poisoning may produce hair loss, stupor, gastrointestinal distress, seizures,
     and headaches, as well as a painful, symmetric, primarily sensory neuropathy.
     Manganese is also a toxin, but long-term exposure to this metal may
     produce parkinsonism rather than a sensory neuropathy. Cyanide was long
     regarded as the cause of an optic neuropathy, but this lethal toxin has probably
     been unjustly ascribed this capability. Mercury poisoning may produce
     a sensory neuropathy, but it is generally associated with paresthesias,
     rather than dysesthesias.

Question 7

453. The most common cause of mononeuropathy multiplex is
     a. Diabetes mellitus
     b. Temporal arteritis
     c. Sarcoidosis
     d. Systemic lupus erythematosus
     e. Periarteritis nodosa

Answer 7

453. The answer is a. (Victor, pp 1396–1399.) Diabetes mellitus is the most
     common cause of mononeuropathy multiplex. In this disorder, individual
     nerves are transiently disabled. The neuropathy usually develops over the
     course of minutes to days, and the recovery of function may require weeks to
     months. Various rheumatoid diseases and sarcoidosis produce similar clinical
     pictures, but temporal arteritis does not typically lead to this type of neuropathy.
     A vascular lesion is believed to be the most common basis for this
     type of neuropathy. If the giant cell arteritis seen with temporal arteritis does
     cause a neuropathy, it is an optic neuropathy with resultant blindness. Unlike
     the peripheral nerve injuries that develop with mononeuropathy multiplex,
     this ischemic optic neuropathy of temporal arteritis produces irreversible
     injury to the affected cranial nerve. The patient who loses vision as part of
     temporal arteritis does not recover it.

Question 8

454. A very thin elderly woman complains of left-sided neck pain. Her
     family attempted to give her a deep intramuscular injection of steroids. She
     complains acutely of pain radiating down her arm and develops a wristdrop.
     The probable site of injection is the
     a. Posterior cord of the brachial plexus
     b. Medial cord of the brachial plexus
     c. Lateral cord of the brachial plexus
     d. T1 spinal root
     e. C5 spinal root

Answer 8

454. The answer is a. (Victor, p 1428.) The radial nerve supplies the
     extensors of the wrist and derives from the posterior cord of the brachial
     plexus. The brachial plexus arises from C5, C6, C7, C8, and T1. These
     spinal roots form the trunks of the brachial plexus. C5 and C6 form the
     upper trunk; C7, the middle trunk; and C8 and T1, the lower trunk. The
     trunks in turn divide into anterior and posterior divisions, which associate
     into cords: the anterior division of the upper and middle trunks gives
     rise to the lateral cord; the posterior divisions of all the trunks give rise to
     the posterior cord; and the anterior division of the lower trunk gives rise
     to the medial cord.

Question 9

455. Injuries limited to the upper brachial plexus are most likely with
     a. Node dissections in the axilla
     b. Pancoast tumor
     c. Birth trauma
     d. Dislocation of the head of the humerus
     e. Aneurysm of the subclavian artery

Answer 9

455. The answer is c. (Victor, p 1428.) The upper brachial plexus includes
     the fifth and sixth cervical spinal roots. Damage to these roots occurs during
     a difficult birth if the head and the shoulder are forced widely apart. This
     could result in stretching or even avulsion of these cervical spinal roots from
     the spinal cord. Node dissection in the axilla or a Pancoast tumor at the apex
     of the lung may produce brachial plexus injury, but it is the lower plexus that
     is vulnerable. Dislocation of the head of the humerus or aneurysm of the subclavian
     artery will typically injure the cords of the brachial plexus, the final
     elements of the plexus from which the principal nerves of the arm arise.

Question 10

456. The most prominent areas of degeneration with Friedreich’s disease
are in the
a. Cerebellar cortex
b. Inferior olivary nuclei
c. Anterior horns of the spinal cord
d. Spinocerebellar tracts
e. Spinothalamic tracts

Answer 10

456. The answer is d. (Rowland, p 645.) Degeneration occurs primarily
     in the spinal cord rather than the cerebellum or brainstem in patients with
     Friedreich’s disease. Both the dorsal and ventral spinocerebellar tracts are
     involved. The other spinal cord structures exhibiting degeneration include
     the posterior columns and the lateral corticospinal tracts.

Question 11

Items 457–460
A 20-year-old ataxic woman with a family history of Friedreich’s disease
develops polyuria and excessive thirst over the course of a few weeks.
She notices that she becomes fatigued easily and has intermittently blurred
vision.

457. The most likely explanation for her symptoms is
     a. Inappropriate antidiuretic hormone
     b. Diabetes mellitus
     c. Panhypopituitarism
     d. Progressive adrenal insufficiency
     e. Hypothyroidism

Answer 11

457. The answer is b. (Rowland, p 646.) More than 10% of patients with
     Friedreich’s disease develop diabetes mellitus. A more life-threatening
     complication of this degenerative disease is the disturbance of the cardiac
     conduction system that often develops. Visual problems occur with the
     hyperglycemia of uncontrolled diabetes mellitus, but even Friedreich’s
     patients without diabetes develop optic atrophy late in the course of the
     degenerative disease.

Question 12

Items 457–460
A 20-year-old ataxic woman with a family history of Friedreich’s disease
develops polyuria and excessive thirst over the course of a few weeks.
She notices that she becomes fatigued easily and has intermittently blurred
vision.

458. The peripheral neuropathy that would be expected to be seen with
     this patient develops in part because of degeneration in
     a. Dorsal root ganglia
     b. Spinocerebellar tracts
     c. Anterior horn cells
     d. Clarke’s column
     e. Posterior columns

Answer 12

458. The answer is a. (Rowland, pp 645–646.) Degenerative changes in
     the peripheral nerves of patients with Friedreich’s disease have several
     bases. Loss of cells in the dorsal root ganglia makes a major contribution to
     this phenomenon. Additional sites of degeneration that affect the sensory
     system include the substantia gelatinosa (Lissauer’s tract) of the posterior
     horn and the dorsal roots themselves. The peripheral neuropathy is
     responsible for the hyporeflexia that is invariably found in the legs of
     affected persons.

Question 13

Items 457–460
A 20-year-old ataxic woman with a family history of Friedreich’s disease
develops polyuria and excessive thirst over the course of a few weeks.
She notices that she becomes fatigued easily and has intermittently blurred
vision.

459. This patient’s condition has been consistently linked to a defect on
     a. Chromosome 21
     b. Chromosome 9
     c. Chromosome 6
     d. The Y chromosome
     e. The X chromosome

Answer 13

459. The answer is b. (Rowland, p 645.) Spinocerebellar atrophy does
     occur linked to chromosome 6, but this is distinct from Friedreich’s ataxia.
     The site of the mutation responsible for Friedreich’s ataxia has been identified
     on chromosome 9, and the gene product, the protein frataxin, has been
     identified. Friedreich’s disease is inherited as an autosomal recessive defect.

Question 14

Items 457–460
A 20-year-old ataxic woman with a family history of Friedreich’s disease
develops polyuria and excessive thirst over the course of a few weeks.
She notices that she becomes fatigued easily and has intermittently blurred
vision.

460. If this patient has children, at what stage of life would they be
     expected to become symptomatic if they inherited Friedreich’s ataxia?
     a. Neonatal period
     b. Juvenile period
     c. Early adulthood
     d. Middle age
     e. Senescence

Answer 14

460. The answer is b. (Rowland, pp 645–646.) Congenital abnormalities
     are rarely evident with Friedreich’s disease, but kyphoscoliosis, pes cavus,
     and other musculoskeletal abnormalities may become evident quite early
     in childhood. Gait difficulty usually develops during childhood in persons
     with Friedreich’s disease. Visual loss, syncope, vertigo, and dysarthria may
     develop during the course of this degenerative disease, but the appearance
     of these other problems may be decades after that of the gait ataxia. Visual
     loss may develop with optic atrophy or retinitis pigmentosa. Strictly cerebellar
     or spinocerebellar tract signs include limb ataxia, nystagmus,
     dysarthria, and gait difficulty. Systemic problems often found in persons
     with Friedreich’s disease include diabetes mellitus and cardiac conduction
     defects.

Question 15

Items 461–463
A 17-year-old male presents with 10 days of progressive tingling
paresthesias of the hands and feet followed by evolution of weakness of the
legs two evenings before admission. He complains of back pain. He has a
history of a diarrheal illness 2 weeks prior. On examination, he has moderate
leg and mild arm weakness, but respiratory function is normal. There is
mild sensory loss in the feet. He is areflexic. Mental status is normal.

461. Spinal fluid analysis in this case is most likely to show
     a. No abnormalities
     b. Elevated protein level
     c. Elevated white blood cell (WBC) count
     d. Elevated pressure
     e. Oligoclonal bands

Answer 15

461. The answer is b. (Victor, p 1382.) This patient’s clinical course is
     consistent with a diagnosis of AIDP, also known as Guillain-Barré syndrome.
     Cerebrospinal fluid is typically under normal pressure in this syndrome,
     and contains no cells in up to 90% of patients. In 10% of patients,
     10 to 50 WBCs, mostly lymphocytes, may appear. Protein levels are generally
     elevated, sometimes to extremely high levels, reflecting the degree of
     inflammatory activity taking place at the level of the spinal roots.

Question 16

Items 461–463
A 17-year-old male presents with 10 days of progressive tingling
paresthesias of the hands and feet followed by evolution of weakness of the
legs two evenings before admission. He complains of back pain. He has a
history of a diarrheal illness 2 weeks prior. On examination, he has moderate
leg and mild arm weakness, but respiratory function is normal. There is
mild sensory loss in the feet. He is areflexic. Mental status is normal.

462. The most frequent preceding infection before the onset of this syndrome
is
a. HIV
b. Cytomegalovirus (CMV)
c. Chlamydia psittaci
d. Mycoplasma pneumoniae
e. Campylobacter jejuni

Answer 16

462. The answer is e. (Victor, pp 1382–1383.) Serologic studies have
     shown that C. jejuni is the most common infection preceding Guillain-Barré
     syndrome. Other less common infections include viral illnesses such as
     CMV, HIV, and Epstein-Barr virus, Lyme disease, and M. pneumoniae infection.
     Guillain-Barré syndrome has also been associated with surgical procedures,
     exposure to thrombolytic agents, lymphoma, and certain vaccines.

Question 17

Items 461–463
A 17-year-old male presents with 10 days of progressive tingling
paresthesias of the hands and feet followed by evolution of weakness of the
legs two evenings before admission. He complains of back pain. He has a
history of a diarrheal illness 2 weeks prior. On examination, he has moderate
leg and mild arm weakness, but respiratory function is normal. There is
mild sensory loss in the feet. He is areflexic. Mental status is normal.

463. Over the course of the following week, he has further evolution of
     weakness involving muscles of the arms, face, and respiration. He is intubated
     and placed in the intensive care unit. Nerve conduction and electromyogram
     (EMG) studies show widespread demyelination. Therapy with
     which of the following may help to speed recovery?
     a. Corticosteroids
     b. Cyclophosphamide
     c. Plasma exchange
     d. Albumin infusions
     e. 3,4-diaminopyridine

Answer 17

463. The answer is c. (Victor, pp 1385–1386.) Treatment of Guillain-Barré
     syndrome is complicated and is best accomplished in an experienced center.
     Specific therapies include plasma exchange and intravenous immunoglobulin,
     which appear to be equivalent in several recent studies. When
     instituted early (within 2 weeks of symptom onset), these modalities can
     reduce the period of hospitalization, the length of time on mechanical ventilation,
     and the time to begin walking again. Corticosteroids do not appear
     to be of benefit. The role of other immunosuppressants, such as cyclophosphamide,
     has not been evaluated. 3,4-diaminopyridine is used in the treatment
     of Lambert-Eaton myasthenic syndrome.

Question 18

Match each clinical scenario with the most likely diagnosis

464. A 26-year-old woman develops the acute onset of left shoulder pain.
     Over the following week, she develops weakness in the proximal left arm
     and mild sensory loss. On examination, she has scapular winging and
     marked weakness of the left deltoid, biceps, and triceps muscles. The right
     side is normal, as are her legs. Mild sensory loss in the upper arm is found.
     She has lost her biceps and triceps reflexes. Her brother recently had a similar
     problem. (SELECT 1 DIAGNOSIS)

a. Charcot-Marie-Tooth disease
b. Fabry’s disease
c. Riley-Day disease (familial dysautonomia)
d. Parsonage-Turner syndrome (brachial plexopathy)
e. Meralgia paresthetica
f. Chronic inflammatory demyelinating polyneuropathy (CIDP)
g. Acute intermittent porphyria
h. Reflex sympathetic dystrophy
i. Leprosy
j. Critical illness neuropathy

Answer 18

464. The answer is d. (Victor, pp 1427–1428.) Parsonage-Turner syndrome
     refers to an acute brachial plexopathy. It may also be called brachial
     neuritis or neuralgic amyotrophy. Usually it begins with acute onset of pain
     in the neck, shoulder, or upper arm. This is followed 3 to 10 days later by
     the rapid evolution of weakness affecting the proximal muscles of the arm;
     rarely, the hand or the respiratory muscles may also be affected. Sensory
     loss also occurs. Some cases are bilateral. Usually, systemic signs are absent,
     though mild pleocytosis may occur. The cause is unknown, but the occurrence
     of the syndrome after vaccination or viral infection has led to the
     notion that it is an immunological or autoimmune response of some sort.
     Familial cases also occur with an autosomal dominant pattern.

Question 19

Match each clinical scenario with the most likely diagnosis

465. A 4-year-old Jewish child has a history of poor sucking at birth, as
     well as multiple respiratory infections during childhood. He is of short
     stature and has not been able to eat due to progressive vomiting. On examination,
     strength is normal, but he is hyporeflexic. There is sensory disassociation,
     with loss of pain and temperature sensation and preservation of
     tactile and vibratory sense. The corneas are ulcerated, pupils do not react,
     and he has orthostatic hypotension. (SELECT 1 DIAGNOSIS)

a. Charcot-Marie-Tooth disease
b. Fabry’s disease
c. Riley-Day disease (familial dysautonomia)
d. Parsonage-Turner syndrome (brachial plexopathy)
e. Meralgia paresthetica
f. Chronic inflammatory demyelinating polyneuropathy (CIDP)
g. Acute intermittent porphyria
h. Reflex sympathetic dystrophy
i. Leprosy
j. Critical illness neuropathy

Answer 19

465. The answer is c. (Victor, p 1423.) Familial dysautonomia, or Riley-
     Day disease, is an autosomal recessive disorder that affects primarily Jewish
     children. It is characterized by a small-fiber neuropathy affecting both
     myelinated and unmyelinated small fibers, thereby causing an impairment
     of pain and temperature sensation. Sympathetic and parasympathetic ganglia
     are also affected, causing the autonomic features. The autonomic manifestations
     may include loss of tears on crying, corneal ulceration, absence
     of pupillary reactivity, poor temperature regulation, excessive perspiration,
     abnormalities of blood pressure control, dysphagia, recurrent vomiting,
     and gastric and intestinal dilation. There is absence of the papillae of the
     tongue. There is no effective treatment other than symptomatic.

Question 20

Match each clinical scenario with the most likely diagnosis

466. A 56-year-old woman has slowly worsening numbness and paresthesias
     of the hands and feet, as well as proximal muscle weakness. Bulbar
     muscles are normal. An EMG shows multifocal conduction block, slowing
     of nerve conduction, and minimal loss of amplitude of muscle action
     potentials. Cerebrospinal fluid (CSF) exam shows an elevation in protein to
     260, but no increase in the number of cells. (SELECT 1 DIAGNOSIS)

a. Charcot-Marie-Tooth disease
b. Fabry’s disease
c. Riley-Day disease (familial dysautonomia)
d. Parsonage-Turner syndrome (brachial plexopathy)
e. Meralgia paresthetica
f. Chronic inflammatory demyelinating polyneuropathy (CIDP)
g. Acute intermittent porphyria
h. Reflex sympathetic dystrophy
i. Leprosy
j. Critical illness neuropathy

Answer 20

466. The answer is f. (Victor, pp 1410–1413.) Chronic inflammatory
     demyelinating polyneuropathy (CIDP) is similar to Guillain-Barré syndrome,
     but it takes a slowly progressive or remitting course rather than one
     of acute onset and rapid resolution. It is a polyradiculoneuropathy, implying
     that it affects the proximal portions of the nerves where they exit the
     spinal cord at the root level. This is the reason for the increase in protein,
     indicating an inflammatory disorder affecting nerve roots and causing
     demyelination. Because nerve roots are affected, this chronic neuropathy is
     not limited at onset to the distal feet, as a diabetic or other degenerative
     neuropathy might be. Patients therefore experience paresis and sensory
     loss proximally as well as distally.

Question 21

Match each clinical scenario with the most likely diagnosis

467. A 40-year-old police officer is given pain medications after a femoral
     fracture. One week later, he presents with confusion, psychosis, abdominal
     pain, and vomiting. On exam, he is tachycardic, hypertensive, and febrile.
     He appears delirious. His arms are weak, sensation is relatively preserved,
     and he is areflexic. His wife relates that he had similar episodes before,
     when he was in the military. (SELECT 1 DIAGNOSIS)

a. Charcot-Marie-Tooth disease
b. Fabry’s disease
c. Riley-Day disease (familial dysautonomia)
d. Parsonage-Turner syndrome (brachial plexopathy)
e. Meralgia paresthetica
f. Chronic inflammatory demyelinating polyneuropathy (CIDP)
g. Acute intermittent porphyria
h. Reflex sympathetic dystrophy
i. Leprosy
j. Critical illness neuropathy

Answer 21

467. The answer is g. (Victor, pp 1389–1390.) Porphyric polyneuropathy
     is associated with acute intermittent porphyria, which is a disorder of heme
     310 Neurology
     biosynthesis in the liver resulting from increased production and excretion
     of porphobilinogen and δ-aminolevulinic acid. The skin is not abnormal in
     this disorder. Instead, it is characterized by recurrent attacks of abdominal
     pain, gastroparesis and constipation (due to autonomic neuropathy), psychosis,
     axonal motor neuropathy, and autonomic instability. Seizures and
     syndrome of inappropriate antidiuretic hormone (SIADH) may also occur.
     Attacks may be fatal if respiratory paralysis or cardiac arrest occurs. Attacks
     may be provoked by porphyrinogenic drugs, such as barbiturates, phenytoin,
     sulfonamide antibiotics, and estrogens. These should be avoided in
     such patients. Treatment is best accomplished with use of intravenous
     hematin when supportive measures are not adequate or the case is severe.

Question 22

Items 468–470
For each clinical scenario, select the most likely condition.
a. Diabetes mellitus
b. Sarcoidosis
c. Thiamine deficiency
d. Pyridoxine deficiency
e. Friedreich’s disease
f. Nitrous oxide poisoning
g. Gout
h. Amyloid
i. Abetalipoproteinemia
j. Carcinoma

468. A 49-year-old dentist complains of a pins-and-needles sensation in
     her feet developing over the course of 3 months. Results of her serum
     chemistries, blood count, and urinalysis are all normal, but her hematocrit
     is at the lower limit of normal. She has a positive Lhermitte’s sign (electrical
     pain down the back on flexion of the neck). EMG and NC studies reveal
     slowed conduction in her sensory nerves. There is no family history of similar
     problems. (SELECT 1 CONDITION)

Answer 22

468. The answer is f. (Bradley, p 2119.) Peripheral neuropathy from
     exposure to anesthetic agents is an occupational hazard faced by many
     health care providers. Megaloblastic anemia may develop along with
     peripheral neuropathy in nitrous oxide–induced neuropathy. This hazard
     is greatly increased if the health care worker uses the anesthetic agent as a
     recreational drug, which is a relatively common practice with nitrous
     oxide. Substance abuse involving agents intended for only occasional or
     short-term use, such as anesthetic agents, opiates, and opioids, must be
     rigorously explored with health professionals who develop inexplicable
     neurologic syndromes. Long-term abuse of nitrous oxide may lead to
     numbness, paresthesias, limb spasticity, and ataxia, signs pointing to central,
     rather than peripheral, nervous system damage. The syndrome is difficult
     to distinguish from vitamin B12 deficiency, and appears to result from
     interference with the vitamin B12–dependent conversion of homocysteine
     to methionine.

Question 23

Items 468–470
For each clinical scenario, select the most likely condition.
a. Diabetes mellitus
b. Sarcoidosis
c. Thiamine deficiency
d. Pyridoxine deficiency
e. Friedreich’s disease
f. Nitrous oxide poisoning
g. Gout
h. Amyloid
i. Abetalipoproteinemia
j. Carcinoma

469. A 25-year-old woman with a prior history of visual loss in the left eye
     and a spastic gait develops impaired pain and temperature perception in
     her feet. She was diagnosed with multiple sclerosis (MS) shortly after her
     visual loss. Her left fundus reveals optic atrophy, and her facial movements
     are asymmetric. Chest x-ray reveals large hilar lymph nodes. Mammogram
     reveals no apparent carcinoma. (SELECT 1 CONDITION)

Answer 23

469. The answer is b. (Rowland, p 621.) Early in its evolution, sarcoid
     may be misconstrued as MS, especially if all the obvious deficits can be
     traced to the CNS. Optic atrophy and facial nerve palsies are common in
     sarcoid that gravitates to the nervous system. Peripheral neuropathy does
     not occur as a feature of MS, a strictly CNS disease, but it is still possible to
     have peripheral neuropathy along with MS, especially if the patient has
     been treated with a neurotoxic agent, such as cyclophosphamide.

Question 24

Items 468–470
For each clinical scenario, select the most likely condition.
a. Diabetes mellitus
b. Sarcoidosis
c. Thiamine deficiency
d. Pyridoxine deficiency
e. Friedreich’s disease
f. Nitrous oxide poisoning
g. Gout
h. Amyloid
i. Abetalipoproteinemia
j. Carcinoma

470. A 41-year-old homeless man complains of severe burning in his feet.
     Vibration, position, pain, and temperature senses are all impaired in both
     of his lower extremities up to the level of the midcalf. He admits to drinking
     1 pt of vodka daily. He was operated on in the past for bleeding from
     esophageal varices. (SELECT 1 CONDITION)

Answer 24

470. The answer is c. (Victor, pp 1212–1215.) Thiamine deficiency
     commonly produces a painful sensory neuropathy in persons with alco-
     Peripheral Neuropathy Answers 311
     holism and poor nutrition. This man’s history of esophageal varices
     and acknowledged alcohol abuse makes it highly likely that he has
     alcoholism-associated thiamine deficiency. Other vitamin deficiencies,
     including pyridoxine deficiency, are undoubtedly present, but thiamine
     deficiency is the most likely to evoke a painful neuropathy earliest.
     Dysesthesias and hyperpathia associated with this neuropathy may be so
     severe as to make it impossible for the patient to walk or tolerate any type
     of garment on the feet.