organism from the bowel or result in clinical improvement. Aminoglycosides,
which can cause neuromuscular blockade, should be avoided.
Periodic Paralysis
Familial periodic paralysis is a rare illness, inherited in an autosomal-dominant
fashion, which results in episodes of severe weakness associated with an
abnormality of circulating potassium during attacks. Two major forms of illness
—hyperkalemic and hypokalemic—are recognized. A third type, normokalemic,
has been described but most likely represents a rare variant of the hyperkalemic
variety. Other disorders that can produce weakness and electrolyte abnormalities,
such as use of corticosteroids or diuretics, thyrotoxicosis, hyperaldosteronism,
and renal insufficiency, may mimic the periodic paralyses. The serum potassium
abnormalities in familial periodic paralysis are believed to be epiphenomena of
yet undelineated muscle membrane abnormalities.
Characteristically, a previously well patient develops a flaccid weakness in his
or her trunk and upper thighs, and the weakness gradually involves the remainder
of the skeletal muscles. Deep tendon reflexes are diminished. The attacks last
from hours to days, and between the attacks, muscular strength is usually normal,
although a minority of patients have residual muscular weakness. In both forms
of periodic paralysis, ECG changes consistent with the serum potassium
abnormality may be noted and cardiac arrhythmias may rarely arise.
Hypokalemic periodic paralysis, the most common type, occurs primarily in
adolescents and young adults. Trigger factors include vigorous exercise, heavy
carbohydrate meals, alcohol, and the cold. During an attack, potassium levels are
usually 2 to 2.5 mEq/L. Emergency treatment of hypokalemic periodic paralysis
includes oral, or rarely IV, potassium. Prophylactically, patients should avoid
precipitants such as vigorous exercise or large carbohydrate loads. Recurrences
may be prevented with spironolactone or acetazolamide.
The hyperkalemic form usually begins in the first decade of life, and attacks
occur predominantly during the period of rest after vigorous exercise or after
fasting. Attacks are typically associated with myotonia. The episodes are more
common than in hypokalemic paralysis but often last less than a few hours.

During the attack, plasma potassium level can be moderately elevated, although it
is often in the upper normal range. Attacks of hyperkalemic periodic paralysis are
often brief enough that acute treatment is unnecessary. In severe attacks, inhaled
albuterol and IV calcium gluconate may be helpful. Acetazolamide, thiazide
diuretics, and albuterol have been used for prevention of recurrences.


DISORDERS OF BALANCE (SEE CHAPTERS 15 ACUTE
ATAXIA AND 24 DIZZINESS AND VERTIGO )
Goals of Treatment
Disordered balance has a broad differential diagnosis and is often associated with
symptoms such as nausea, dizziness, vertigo, and ataxia. Ataxia is an inability to
produce smooth, coordinated movements and is typically a sign of cerebellar
dysfunction. Alterations of balance and ataxia can result from dysfunction of the
nervous system at many levels: cerebellum, sensory pathways, posterior columns
of the spinal cord. Ataxia can be a manifestation of motor weakness as seen in
Guillain–Barré. Therefore, early goals of treatment should focus on identifying
the level of nervous system involvement and ruling out life-threatening causes,
intracranial mass lesion, stroke, CNS hemorrhage, CNS infection.
CLINICAL PEARLS AND PITFALLS
Acute ataxia is uncommon but most cases are secondary to a benign
etiology.
Cerebellar dysfunction is the most common cause of ataxia.
Signs of cerebellar dysfunction include the following:
Gait disturbance, truncal ataxia, nystagmus, dysmetria, tremor
MRI is the imaging modality of choice for acute ataxia.
Acute Ataxia
Acute postinfectious cerebellar ataxia (APCA) and intoxication are the two most
common causes of acute ataxia in children. APCA is characterized by the acute
onset of unsteadiness in a previously well child. It is seen primarily between the

ages of 1 and 4 years but can occur at any time during childhood. The exact cause
of the illness is unclear; however, it is believed to be a parainfectious or
postinfectious demyelinating phenomenon and likely represents a localized form
of postinfectious encephalitis. Historically and in regions where varicella is
prevalent, primary varicella is the most common cause of APCA. Other infections
implicated include infectious mononucleosis, enteroviruses, HSV, influenza,
Mycoplasma, and Q fever. Ataxia is usually seen 5 to 10 days after the onset of
illness, although symptoms may be delayed for up to 3 weeks.


The child develops acute truncal unsteadiness with a variable degree of distal
motor difficulty, such as tremor and dysmetria. Dysarthria and nystagmus are
variably present. Some children have nausea and vomiting, presumably caused by
vertigo. Headache is rare.
When acute ataxia follows a viral illness in a child with no other neurologic
findings, the diagnosis of APCA may be made on clinical grounds. In atypical
cases, CT or MRI may be necessary to rule out a cerebellar mass. LP is not
usually necessary in typical cases; if performed, it reveals a mild CSF pleocytosis
in approximately half of the cases.
Treatment is supportive. Resolution of symptoms is complete in most children
within 2 weeks of onset, but mild residual neurologic deficits have been reported
in 10% to 30% of cases. Varicella-associated cases appear to have the most
benign prognosis.
Cerebellitis and ADEM are the two other postinfectious syndromes that present
with acute ataxia in children. Acute cerebellitis presents with ataxia and altered
mental status to suggest increased ICP. ADEM and multiple sclerosis can present
with acute ataxia and have multifocal demyelinating changes on MRI, but ADEM
presents with encephalopathy.
Benign Paroxysmal Vertigo
Benign paroxysmal vertigo is an illness that affects children primarily between 1

and 4 years of age, although it can occur any time during the first decade. It
manifests with acute episodes of dizziness and imbalance, lasting seconds to
minutes. Between episodes, the child is asymptomatic. During the spell, the child
characteristically becomes frightened and pale but does not lose consciousness.
He or she may have associated nausea, vomiting, or visual disturbance. The
physical examination is usually normal except for nystagmus, which may be
present. Although the cause of this illness is unknown, it is believed to be a
migraine variant. Many children go on to develop more typical migraine
headaches later, and there is often a family history of migraine disease. As the
name suggests, the course of benign paroxysmal vertigo is self-limiting and
benign, and treatment is supportive.

MOVEMENT DISORDERS
Goals of Treatment
Involuntary movements are components of many CNS disorders, tend to be
complex, and are diagnosed by associated neurologic findings. Classifying


movements into specific subtypes, based on the character, predominant anatomic
localization, rhythmicity, and frequency, can be useful in deducing the cause of
the disorder. Additionally, the type of movement can suggest the location of CNS
dysfunction ( Table 97.9 ).
CLINICAL PEARLS AND PITFALLS
Tics are the most common movement disorder in children.
Acute dystonia in children is almost always associated with exposure to
an antidopaminergic medication.
Treatment with prednisone can decrease the duration of chorea and
the time to full remission in patients with Sydenham chorea.
Acute Dystonia
Dystonia is marked by involuntary, sustained muscle contractions, typically of the

neck and trunk, that cause twisting movements and abnormal postures. In
generalized dystonia, the head is usually deviated to the side and there is
grimacing of the face. Acute dystonia in children is nearly always the result of
exposure to an antidopaminergic agent such as a neuroleptic, antiemetic, or
metoclopramide. Chronic dystonias are rare but may be seen as an isolated
disorder or as a manifestation of cerebral palsy. Dystonia must be differentiated
from torticollis, an abnormal tilt of the head and neck usually resulting from
irritation or spasm of the sternocleidomastoid muscle (see Chapter 49 Neck
Stiffness ). Another clinically similar condition is Sandifer syndrome, which
describes intermittent arching of the back and neck in infants with
gastroesophageal reflux.
TABLE 97.9
CATEGORIZATION OF MOVEMENT DISORDERS