peripheral neuropathies Flashcards
peripheral neuropathies
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
- 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.
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.
- 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
- 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
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.
- 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
- 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.
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.
- 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)
- 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
- 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
.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.
- 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
- 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.
- The most common cause of mononeuropathy multiplex is
a. Diabetes mellitus
b. Temporal arteritis
c. Sarcoidosis
d. Systemic lupus erythematosus
e. Periarteritis nodosa
- 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.
- 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
- 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.
- 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
- 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.
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
- 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.
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.
- The most likely explanation for her symptoms is
a. Inappropriate antidiuretic hormone
b. Diabetes mellitus
c. Panhypopituitarism
d. Progressive adrenal insufficiency
e. Hypothyroidism
- 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.
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.
- 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
- 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.
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.
- 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
- 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.
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.
- 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
- 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.
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.
- 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
- 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.
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
- 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.
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.
- 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
- 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.
Match each clinical scenario with the most likely diagnosis
- 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
- 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.
Match each clinical scenario with the most likely diagnosis
- 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
- 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.
Match each clinical scenario with the most likely diagnosis
- 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
- 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.
Match each clinical scenario with the most likely diagnosis
- 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
- 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.
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
- 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)
- 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.
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
- 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)
- 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.
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
- 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)
- 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.
