Pediatric Examination and Board Review (17 page)

An abnormality of the myelin sheath can be seen, as well, in diseases of both children and adults. The most common demyelinating disorder is Landry-Guillain-Barré (LGB) syndrome. LGB is a postinfectious destruction of the myelin such that nervous transmission is significantly slowed and ultimately functionally stops. Unlike botulism, this presents most often as an ascending weakness. However, like botulism, Guillain-Barré syndrome may result in respiratory insufficiency requiring mechanical ventilation.

In some diseases, acetylcholine metabolism can be blocked or its attachment to the motor endplate can be altered. In the case of botulism, the toxin causes irreversible inhibition of the release of acetylcholine at the presynaptic nerve terminal. Complete resolution of clinical symptoms requires that new nerve terminals sprout and normal release of acetylcholine resumes.

Beyond the neuromuscular receptor lies the muscle itself. A variety of disorders affecting the myocyte might present with generalized weakness and can be classified as either a myopathy or myositis. The differential diagnosis of myopathy is beyond the scope of this discussion but is generally marked by the elevation of muscle enzymes creatine phosphokinase and aldolase, and muscle tenderness. Constipation is rare.

10.
(C)
When aminoglycosides are given to treat intercurrent infection, they can potentiate the muscle weakness and therefore are relatively contraindicated. Aminoglycosides and hypermagnesemia augment the symptoms of botulism by causing neuromuscular failure by presynaptic blockade of acetylcholine release.

11.
(E)
Treatment for infant botulism is largely supportive and includes close monitoring in an intermediate or intensive care unit setting to detect progressive respiratory insufficiency. Human-derived botulinum antitoxin, also known as botulinum immunoglobulin (BIG), should be administered as well. In a controlled trial from the University of Pennsylvania, administration of BIG decreased the need for mechanical ventilation and shortened the duration of hospitalization when compared with patients in the control group. Antibiotics are helpful only to treat nosocomial infections that arise in a hospitalized patient and do not change the course of botulism.

12.
(C)
Werdnig-Hoffmann disease or infantile spinal muscular atrophy can present with hypotonia in infancy. These infants would be expected to have weakness, wasting, and absence of tendon reflexes. Tongue fasciculation might also be observed. Constipation would be rare.

13.
(A)
The neurologic examination will lead you down the path of a myelopathy, neuropathy, or a myopathy. Nerve conduction and electromyographic studies can confirm your suspicion of the anatomic location of the pathology. In Werdnig-Hoffman, the interruption in neuromuscular transmission is at the anterior horn cell. In the adult patient, the most common disease affecting the anterior horn cell is amyotrophic lateral sclerosis (Lou Gehrig disease).

14.
(A)
In polio, the interruption is also at the anterior horn cell. Beyond the anterior horn cell level, a variety of neuropathies can interrupt peripheral nervous transmission. Most do not present with generalized weakness. Nor do affected patients present in the first 4 months of life.

15.
(D)
An abnormality of the myelin sheath can be seen as well in diseases of both children and adults. The most common demyelinating disorder is a lateral geniculate body (LGB) syndrome. Guillain-Barré syndrome is a postinfectious destruction of myelin such that nervous transmission is significantly slowed and ultimately functionally stops. Unlike botulism, this presents most often as an ascending weakness. However, like botulism, Guillain-Barré syndrome may result in respiratory insufficiency requiring mechanical ventilation.

16.
(B)
Normal functioning of the neuromuscular endplate may also be temporarily disrupted by medications commonly used in the operating room. Nondepolarizing muscle relaxants such as pancuronium bind reversibly to the motor endplates and prevent neuromuscular transmission for a short period of time. The reversibility of this process distinguishes it from other pathologic disease states, such as myasthenia gravis. In myasthenia, antibodies directed against the acetylcholine receptor on the motor endplate result in postsynaptic inhibition of neuromuscular transmission. This inhibition results in weakness, which worsens with repetitive stimulation of the endplate.

S
UGGESTED
R
EADINGS

Bartlett JC. Infant botulism in adults.
N Engl J Med.
1986;315(4):254-255.

Nelson KE. Editorial: The clinical recognition of botulism.
JAMA.
1979;241(5):503-504.

L’Hommedieu CL, Polin RA. Progression of clinical signs in severe infant botulism.
Clin Pediatr.
1981;20(2):90-95.

Domingo RM, Haller JS, Gruenthal M. Infant botulism: two recent cases and literature review.
J Child Neurol.
2008;23(11):1336-1346.

Chia JK, Clark JB, Ryan CA, et al. Botulism in an adult associated with food-borne intestinal infection with
Clostridium botulinum
.
N Engl J Med.
1986;315(4):239-240.

CASE 8: A 5-YEAR-OLD BOY WITH FEVER, DROOLING, AND STRIDOR

A 5-year-old boy presents to the emergency department with a 12-hour history of fever and drooling. He was well previously. His temperature is 39.5° C and he appears toxic. There have been no other symptoms and no sick contacts. He is visiting his aunt in the United States and lives in Guatemala. He has received no immunizations.

On physical examination, the heart rate is 120 bpm, the respiratory rate is 26, and the room-air blood oxygen saturation is 92%. The child has marked inspiratory stridor and refuses to swallow. He is sitting, leaning forward slightly, and refuses to lie down for the examination.

A chest radiograph is normal. The leukocyte count is 28,000/mm
³
with a significant left shift.

SELECT THE ONE BEST ANSWER

1.
What is the best initial diagnostic procedure?

(A) a radiograph of the neck

(B) an evaluation of the upper airway by an otolaryngologist

(C) ultrasonography of the neck

(D) a nasopharyngeal aspirate for culture

(E) a chest radiograph

2.
In this case, if the diagnosis is epiglottitis, what is the likely pathogen?

(A) a coagulase-negative staphylococcus

(B)
Streptococcus pneumoniae

(C)
Haemophilus influenzae

(D) parainfluenza virus

(E) influenza virus

3.
If the diagnosis of epiglottitis is confirmed in the operating room by direct visualization by an otolaryngologist, the best next step would be

(A) a transfer to the intensive care unit (ICU) with supplemental humidified oxygen

(B) an endotracheal intubation before transfer to the ICU

(C) a tracheostomy before transfer to the ICU

(D) a transfer to the ICU with administration of corticosteroids

(E) admission to the pediatric floor for intravenous (IV) antibiotics

4.
In the United States, epiglottitis is best characterized as

(A) seasonal

(B) sporadic

(C) largely eradicated by immunization

(D) endemic

(E) none of the above

5.
The differential diagnosis of the febrile illness described includes all of the following except

(A) bacterial tracheitis

(B) retropharyngeal abscess

(C) peritonsillar abscess

(D) maxillary sinusitis

(E) odontogenic abscess

6.
In bacterial tracheitis, the most likely pathogen is

(A)
Staphylococcus aureus

(B)
Haemophilus influenzae

(C)
Neisseria meningitidis

(D)
Streptococcus pneumoniae

(E)
Moraxella catarrhalis

7.
In the case of a patient with peritonsillar abscess, which of the following is true?

(A) operative intervention is often needed

(B) IV antibiotics are sufficient treatment

(C) outpatient treatment with oral antibiotics is effective

(D) endotracheal intubation is required for at least a week of antibiotic therapy to avoid airway obstruction

(E) A and D

8.
In a febrile toxic-appearing patient with a maxillary sinusitis and altered sensorium, management includes

(A) IV antibiotics for 1 week

(B) oral antibiotics for 3 weeks

(C) scheduled outpatient endoscopic sinus surgical drainage

(D) evaluation of CSF for possible meningitis, then a course of IV antibiotics

(E) watchful waiting

9.
A true statement about differentiating croup from epiglottitis is

(A) the child with viral croup is often older than the patient with epiglottitis

(B) the child with viral croup always has a more abrupt onset of stridor than the patient with epiglottitis