Pediatric Examination and Board Review (231 page)

14.
(D)
This child has one of the congenital myopathies, which represent a diverse group of skeletal muscle disorders. The group of disorders is represented in this question by central core disease, nemaline myopathy, and centronuclear myopathy. Most patients with congenital myopathy have a benign clinical course with some cases occurring in late childhood or adulthood. The congenital myopathies are differentiated from one another based on characteristic pathologic findings of the skeletal muscle, predominantly affecting type 1 myofibers. The congenital myopathies often come to mind in a floppy child without reflexes. The myopathies can have overlapping clinical features with each other, as well as with CMD. As a result, in the absence of a muscle biopsy, it may be difficult to distinguish one from the other. The clinical history presented in this case suggests X-linked recessive transmission. Of the choices listed, only centronuclear (myotubular) myopathy has X-linked recessive transmission. In fact, the X-linked or neonatal form of centronuclear myopathy is particularly severe. Neonatal onset is associated with a rapidly progressive course in which infants often develop respiratory complications leading to death. Other forms of centronuclear myopathy exist with onset occurring in late infancy and childhood (autosomal recessive transmission) or adulthood (autosomal dominant transmission). The name
myotubular myopathy
is generally used for the severe X-linked form of the disease. As its name implies, centronuclear myopathy is characterized by the presence of centrally located nuclei in small type 1 myofibers on histology. The first congenital myopathy described was central core disease due to palely stained cores within type 1 myofibers on histology. The disease is inherited as an autosomal dominant trait. Nemaline myopathy was the second congenital myopathy to be defined based on its distinctive morphologic feature of myogranules or “rods,” located beneath the sarcolemma, stained reddish/purple on trichrome staining. However, nemaline rods are not entirely specific to nemaline myopathy. Autosomal dominant and recessive inheritance has been observed for this disorder. Spinal muscular atrophy type 1 (Werdnig-Hoffmann disease) is an autosomal recessive disorder characterized by the loss of lower motor neurons in the anterior horn of the spinal cord. It is the most severe of the 3 types, resulting in death by 2 years of age from respiratory failure or infection. Affected infants have severe weakness of the intercostal muscles and limbs, tongue fasciculations, and polyminimyoclonus (a fine tremor) of the hands. Deep tendon reflexes are usually absent.

15.
(A)
Fasciculation of the tongue, as well as atrophy, occurs with injury to the ipsilateral hypoglossal nucleus or hypoglossal nerve (cranial nerve XII). Fasciculations are commonly seen in spinal muscular atrophy type 1.

16.
(C)
Many cases of MERRF are caused by mutations to the tRNA Lys gene of mitochondrial DNA. However, there does appear to be genetic heterogeneity because not all patients with MERRF have this mutation. Any patient with seizures, myoclonus, and a myopathy should raise the suspicion of a mitochondrial disorder such as MERRF.

17.
(B)
As muscle is a highly energy-dependent tissue, any disruption of energy metabolism can result in a myopathy. Pompe disease (type 2 glycogenosis), a disorder of glycogen metabolism, is caused by an acid maltase deficiency and refers to the more severe generalized disease of infancy. A more benign form, with onset in childhood or adulthood, also exists. Patients with Pompe disease present with weakness, hypotonia, macroglossia, hepatomegaly, and cardiomegaly.

18.
(A)
McArdle disease (type 5 glycogenosis), a cause of recurrent myoglobinuria, is caused by a myophosphorylase deficiency. Patients experience myoglobinuria following exercise. Resting serum creatine kinase levels are increased.

S
UGGESTED
R
EADING

Escolar DM, Leshner RT, Swaiman KF. Muscular dystrophies. In: Swaiman KF, Ashwal S, Ferriero DM, eds.
Pediatric Neurology: Principles & Practice.
4th ed. Philadelphia, PA: Mosby; 2006:1969.

Mathews KD. Muscular dystrophy overview: genetics and diagnosis.
Neurol Clin North Am.
2003;21:795-816.

Riggs JE, Bodensteiner JB, Schochet SS Jr. Congenital myopathies/dystrophies.
Neurol Clin North Am.
2003;21:779-794.

Wolfe GI, Barohn RJ. Diseases of the neuromuscular junction. In: Swaiman KF, Ashwal S, Ferriero DM, eds.
Pediatric Neurology: Principles & Practice.
4th ed. Philadelphia, PA: Mosby; 2006:1942.

CASE 135: A 7-YEAR-OLD BOY WITH HEAD JERKS

A 7-year-old boy with attention deficit disorder comes to your clinic for a routine follow-up examination. During the examination, you notice occasional eye blinking and right-sided head jerks. His mother states that she has noticed these movements for approximately 6 months. A year ago, the patient would repetitively open his mouth wide open, as if to “stretch his jaw.” The movements seem to come and go but never disappear for more than 2 months. The movements are infrequent, and she always assumed they were behavioral or “part of his allergies.” The child states that the movements are involuntary. On questioning his mother further about the allergies, you learn he has periods of sniffing and throat clearing. Her previous pediatrician stated these were symptoms of seasonal allergies. The movements never occur during sleep and are exacerbated by stress. The patient states that if he tries hard enough, he can suppress the behaviors for brief periods of time. There is no history of seizure-like activity. There is a family history of psychiatric illness on both sides of the family. On review of his past medical history, you note he has not had any history of streptococcal throat infections. His physical examination is normal.

SELECT THE ONE BEST ANSWER

1.
In further evaluating this child it is important to ask which of the following questions?

(A) “what medications does your child currently take?”

(B) “does your child suffer from any sleep disorders?”

(C) “are the movements bothersome to the child or do his friends comment on the movements?”

(D) “does your child suffer from any psychiatric conditions, such as obsessive-compulsive disorder, depression, or anxiety?”

(E) all of the above

2.
His mother states that he is currently taking an antihistamine for his allergies and denies any history of psychiatric illness. The most likely diagnosis of this child’s medical problem is which of the following?

(A) seizure disorder

(B) Wilson disease

(C) Tourette syndrome

(D) allergic rhinitis

(E) anxiety disorder

3.
His mother states that she was given a prescription for methylphenidate to treat his ADHD but that he hasn’t started taking it yet. In counseling the mother regarding the use of this medication, which of the following statements is appropriate?

(A) “methylphenidate is best given before the patient goes to bed”

(B) “methylphenidate will also help control the motor movements”

(C) “there is a chance that the methylphenidate will exacerbate the movements and, as a result, you should consider a medication that treats both the tics and ADHD, such as clonidine”

(D) “an EEG should be obtained before starting the medication”

(E) none of the above

4.
The
Diagnostic and Statistical Manual of Mental Disorders, 4th edition
, diagnostic criteria for Tourette syndrome include all of the following except

(A) onset must have occurred before the age of 18 years

(B) the patient must demonstrate multiple motor tics

(C) the duration of symptoms must be longer than 6 months

(D) vocal tics must be present

(E) the disorder is not the result of another medical condition

5.
Which of the following neuropsychological problems are associated with Tourette syndrome?

(A) OCD

(B) ADHD

(C) depression

(D) behavioral problems

(E) all of the above

6.
On further questioning, you learn that the patient frequently washes his hands because he believes they are contaminated with harmful germs. He frequently checks to make sure the windows are locked to the point that he cannot leave the house until he has checked each window. The most appropriate treatment for this disorder is which of the following medications?

(A) clonazepam

(B) dextroamphetamine

(C) risperidone

(D) desipramine

(E) fluoxetine

7.
Which of the following statements is false regarding Tourette syndrome?

(A) females are more commonly affected than males

(B) the mean age of onset is between 6 and 7 years of age

(C) an MRI of the brain is most often normal in these patients

(D) treatment of tics should be reserved for those patients who have failed nonpharmacologic treatments and in whom the movements are disturbing or functionally disabling

(E) in terms of prognosis, tics will remain stable or increase in approximately a quarter of the patients, whereas most will show at least some improvement into adulthood

8.
All of the following have been used in the treatment of tic disorders except

(A) pimozide