Hidden Impact

History and Physical

A 3-year-old previously healthy male was referred to the emergency department with a sudden-onset unsteady gait that persisted for 8 hours. He had no headache or neck pain and no recent history of infections, vaccinations, or toxic exposures. However, 3 days earlier, he had been a restrained passenger in a car that suddenly stopped. There was no family history of migraine, gait disturbances, psychiatric disorders, or early-onset stroke. Physical examination on admission showed a weight of 16 kg (50th–75th percentile), height 85 cm (5th–10th percentile), head circumference 51 cm (75th–90th percentile), blood pressure 91/46 mmHg (50th percentile), and pulse 88 bpm. The patient was fully alert and oriented. Cranial nerve examination, fundoscopy, and motor and sensory examination were all normal. Cerebellar examination revealed gait and limb ataxia. Language and speech were normal. Deep tendon reflexes were normal.

Diagnostic Workup

Head CT performed at 11 hours after symptom onset was unrevealing. Brain MRI 28 hours after onset showed an acute right anterior cerebellar infarct in the territory of the superior cerebellar artery (SCA) ( Fig. 22.1A–C ). Neck MRA showed mild right vertebral artery irregularity ( Fig. 22.1D ). Lumbar puncture and CSF cultures were normal. Blood tests and prothrombotic studies were normal. Toxins in urine were negative. On day 4 of admission, the patient recovered completely. He was started on anticoagulant therapy and discharged after 1 week on antiplatelet therapy.

An illustration shows four panels marked A, B, C, and D, of which the first three display brain M R I scans and panel D shows neck Magnetic Resonance Angiography showing vertebral irregularity. — Fig. 22.1

Follow-up brain MRI 4 months later showed a new asymptomatic (silent) infarct in the left PICA (posterior inferior cerebellar artery) territory ( Fig. 22.2 ). CT angiography was performed and showed bilateral vertebral artery irregularity and pseudoaneurysms ( Fig. 22.3 ). The patient was switched to oral anticoagulant therapy for 6 months, followed by aspirin for 2 more years, with no further findings on imaging.

An illustration of three axial brain scans labeled A to C. Arrows in A and B point to the left cerebellum. An arrowhead in C points to the right cerebellum. — Fig. 22.2

An illustration shows a cross sectional and coronal neck scan with arrows that marks abnormalities in the vertebral arteries. — Fig. 22.3

Clinical Differential Diagnosis

The most common cause of acute ataxia in children is acute cerebellar ataxia following viral or bacterial illness, which is thought to be an autoimmune process with cross-reactivity of pathogenic antibodies. This is most commonly described with varicella or Epstein-Barr virus, characterized by rapid-onset ataxia during the acute or convalescent phase of disease. Lumbar puncture usually reveals mild pleocytosis.

Other etiologies of ataxia include toxins (alcohol, barbiturates, antiepileptic drugs) and trauma.

Neuroinflammatory disorders, such as acute disseminated encephalomyelitis (ADEM), usually present with encephalopathic features such as impaired consciousness and other neurological symptoms such as motor deficits. Miller-Fisher syndrome is a cranial nerve variant of Guillain-Barré syndrome characterized by postinfectious acute ataxia, areflexia, and ophthalmoplegia. Cerebrospinal fluid shows albuminocytological dissociation, and anti-GQ1b antibody may be positive.

Metabolic disorders that can present with episodic ataxia include urea cycle disorders, mitochondrial disorders, and congenital disorders of glycosylation.

Imaging Differential Diagnosis

Cerebellitis: MRI findings of acute cerebellitis have been categorized into bihemispheric cerebellitis, hemicerebellitis, and cerebellitis with encephalitis. There is edema of the involved regions and no or minimal linear contrast enhancement ( Fig. 22.4 ). Typically, the deep gray nuclei are spared, in contrast to metabolic disorders that disproportionately involve gray matter structures.