Peripheral Neuropathy Flashcards
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 spon-taneously 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.
- 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
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.
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 spon-taneously 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
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.
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 spon-taneously 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
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 foot-drop, and irritation of spinal roots to the sciatic nerve produces the foot-drop 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.
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 spon-taneously 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)
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
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
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
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 wrist-drop. 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
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
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.
- 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
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.
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
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.
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
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.
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
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.
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
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.
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
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.
