Hooven animals are complicated creatures (just like humans). They can be majestic, but rambunctious. They can be wild, yet tamed. In medicine, we often try to distinguish between them: Horses versus Zebras. While searching among the horses for the zebras, we may have in mind that the zebras are rare, which can be true on an individual basis; however, when the group you are searching through is large, the absolute number of zebras can be substantial (see Inborn Errors of Metabolism). The trick is to keep a vigilant eye open, trying to detect even the most subtle of stripes. One of those stripes that will catch your attention is ataxia. Let us take a moment to review one of the common “zebras” in children- Acute Cerebellar Ataxia:

Acute Cerebellar Ataxia: Basics

• Acute cerebellar ataxia is a common pediatric neurologic problem.
  • Incidence of 1 in 100,000 – 500,000.

• Some causes of ataxia in children: [Thakkar, 2016]
  • Post-infectious Cerebellar Ataxia – (~30 – 60%)
  • Drug Intoxication (~8%)
    • ex, Alcohol, Benzos, Heavy Metals, CO poisoning, Anticonvulsants
  • Opsoclonus Myoclonus Ataxia (~8%)
    • Rare, but a true medical emergency!
    • May be misdiagnosed as benign post-infectious cause at first.
    • Has severe ataxia, opsoclonus (chaotic ocular movements), and myoclonus.
    • Is a Paraneoplastic disorder (often neuroblastoma)! [Tate, 2005]
  • Acute Cerebellitis (~2%)
    • Most severe end of the spectrum of cerebellar inflammation/infection. [Rossi, 2016]
    • Previously, “Acute Cerebellitis” was used interchangeably with Post-infectious, But:
      • Acute Cerebellitis has a distinctly worse disease course.
      • Has abnormalities on brain MRI.
      • Can lead to rapid posterior fossa edema and lead to morbidity and mortality.
  • Cerebellar Stroke (~2%)
    • Yes, stroke can occur in children.
    • Look for risk factors, like:
      • Sickle Cell Disease
      • Nephrotic Syndrome
      • Lupus
  • Acute Disseminated Encephalomyelitis (ADEM) (~2%)
    • Immunologically mediated inflammatory disease
    • Polyfocal neurological signs (multiple sites involved in CNS)
    • Rapid onset of encephalopathy (altered mental status)
  • Meningitis (<1%)
  • Cerebral Venous Thrombosis (<1%)
  • Miller Fisher Syndrome (<1%)
  • Hereditary conditions (ex, Ataxia-telangiectasia)

Acute Cerebellar Ataxia: Post-infectious

• The most common cause of acute cerebellar ataxia in children is post-infectious cerebellar ataxia. [Thakkar, 2016; Rossi, 2016]
  • Generally seen in kids younger than 6 years.
  • Most common among 2 – 4 year olds.

• Presents in a relatively well appearing child who has: [Doan, 2016]
  • Lack of coordination of movement NOT due to paresis,
  • Alterations in tone,
  • Sensory loss, and/or
  • Involuntary movements
• Often, symptoms begin suddenly.
• NOT associated with fever, seizures, change in mental status, or other systemic signs. [Doan, 2016]

• Is a diagnosis of exclusion, because other ominous conditions can present similarly.

• Commonly associated infections:
  • Varicella [Fursow, 2013]
    • Chickenpox is frequently the cause of acute cerebellar ataxia in the immunosuppressed patient. [Fursow, 2013]
    • Varicella vaccination, however, is protective. [van der Maas, 2009]
  • Epstein-Barr virus
  • Echovirus
  • Enterovirus (Coxsackievirus)

• Work-up is generally negative!
  • Cerebrospinal fluid analysis has low diagnostic yield. [Thakkar, 2016]
    • Certainly CSF analysis is helpful if you are more concerned for meningitis or encephalitis.
    • LP, if performed, should wait until after imaging to rule-out posterior fossa mass or edema. [Doan, 2016]
  • Imaging is typically normal. [Thakkar, 2016; Doan, 2016]
    • MRI is preferred given higher resolution and superior imaging of posterior fossa. [Rossi, 2016]
    • CT should be obtained for patients with altered mental status, atypical disease course, asymmetric focal neurologic deficits, or when hemorrhage or mass is higher on the Ddx list.
  • “Basic Labs” will be normal.
    • Glucose is always worth checking!
    • Electrolytes and urine catecholamines may be useful if concern for opsoclonus-myoclonus.
  • Urine Tox screens should be considered, particularly in the toddlers who like to eat random items in the house. [Doan, 2016]

• Patient recover without lasting sequelae. [Thakkar, 2016]
  • Usually has resolution of symptoms in 2-8 weeks.
  • Complete resolution by 2-3 months.

Moral of the Morsel:

• Zebras are common collectively! Look for the subtle stripes!
• Make kids walk! Yes, toddlers do “toddle,” but shouldn’t be ataxic!
• Look at the eyes! Nystagmus may be seen with benign conditions, but opsoclonus is scary!

References