Acute cerebellar ataxia in children

Stephen L Nelson Jr MD PhD (

Dr. Nelson of Tulane University School of Medicine received consulting fees from BioMarin and Supernus for speaking engagements.

Michael V Johnston MD, editor. (

Dr. Johnston of Johns Hopkins University School of Medicine has no relevant financial relationships to disclose.

Originally released March 14, 1994; last updated October 3, 2018; expires October 3, 2021

This article includes discussion of acute cerebellar ataxia (in children), acute cerebellitis, and acute postinfectious cerebellitis. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.


Acute cerebellar ataxia is a relatively common disorder among children and is usually observed following an acute viral illness or vaccination. The usual presentation includes sudden onset of unsteadiness, gait difficulties, and nystagmus. The clinical features are similar to that of other acute ataxias in childhood, so it is important to consider other potentially serious and important conditions in the initial evaluation of these children. The prognosis is excellent, with most children obtaining a full recovery within weeks to months, and the treatment is typically supportive.

Key points


• The peak incidence of acute cerebellar ataxia is in children between 2 and 4 years old, most commonly presenting as truncal, rather than extremity, ataxia.


• Up to 20% of patients have no prodrome, and in others, the prodrome can last from weeks to months.


• Historically, the most commonly identified cause of acute cerebellar ataxia has been varicella; however, multiple other viral and bacterial causes, such as Epstein-Barr virus, influenza, and Mycoplasma, have been reported.


• More than 90% of children recover, and treatment is typically supportive.


• Although typically bilateral, cases of hemicerebellitis have been reported, which may be confused with tumors on neuroimaging.


• Cerebellar swelling can result in fatal or near-fatal outcome, and prompt recognition and treatment is essential in these cases.

Historical note and terminology

In 1905, Batten published a seminal article on ataxia in children in which he subdivided ataxia into 3 categories: cases in which ataxia was noted early in life and tended to improve with age, designated “congenital ataxia”; cases in which there was a gradually developing ataxia in a previously well child, termed “progressive ataxia”; and ataxia that developed after some acute illness in otherwise healthy normal children, which he termed “acute ataxia” or “encephalitis cerebelli” (Batten 1905). He described cases of acute ataxia as follows:

A child perfectly healthy and of good intellectual development is taken ill with some acute febrile disease, which may assume some definitive type, such as measles, or may be assigned to the more indefinite influenza. A period of unconsciousness may be present, but general convulsions seldom occur. The child is kept in bed for a few days and seems to be making a normal convalescence. When, however, the child is sat up in bed, it is found that he is unable to maintain his balance. There is marked incoordination of the hands, and, if stood on his feet, he is wildly ataxic. It may be noticed at the same time that his speech is affected. In a few days his general health is restored, but he remains as ataxic as ever. Recovery now gradually takes place, and although in a few cases recovery may be complete in 2 or 3 months, in most cases the period of recovery extends over months, and it may be two or three years.

Most of the cases were noted to follow an infection, such as typhoid fever, measles, pertussis, scarlatina, and variola. He postulated, “The lesion is of vascular origin.”

Griffith published a series of papers between 1916 and1921 reporting the clinical findings of 4 of his patients and summarizing the literature to date for an additional 27 patients (Griffith 1921). Unsteadiness of gait, ataxia of trunk and head, and incoordination of the extremities were the most commonly noted findings. In 24 of 31 cases, nervous system involvement occurred during or immediately after an infection: measles encephalitis in 8 cases, influenza in 5 cases, and typhoid fever in 4 cases. He felt that these cases represented nonsuppurative encephalitis, in which the principal component of the nervous system affected was the cerebellum, and, thus, he designated the condition “acute cerebellar encephalitis” or “acute cerebellar ataxia.” In 25% of patients, the ataxia slowly cleared by 6 months, but it persisted for years in some; additionally, about 25% of patients had some persisting “mental deficit.”

In 1936, Ely reported that ataxia could be associated with variola, varicella, and scarlatina (Ely 1936). In 1944, Klingman and Hodges reported a series of 7 patients, 4 of which had onset of ataxia with no infection by history, exam, or laboratory testing, casting doubt on the infectious association (Klingman and Hodges 1944). In 1950, Shanks published a series on 39 children with cerebellar ataxia seen between 1929 and 1949, in which he divided the patients into 2 categories of onset: acute and insidious (Shanks 1950). He felt that the insidious-onset patients represented degenerative ataxias of genetic origin, as evidenced by progressive ataxia and cerebellar degeneration over time. In contrast, he felt that the acute ataxia cases represented postinfectious encephalitis/encephalomyelitis, although only 6 of 22 patients had demonstrable temporal infections or vaccinations. He stressed that the majority of these patients had complete recovery, whatever the etiology. In 1953, Goldman and Waldman reported on 3 cases, all of which demonstrated complete recovery within 1 month of acute ataxia (Goldman and Waldman 1953).

Cottom published a series of 7 cases of acute cerebellar ataxia in 1957, and in reviewing the literature, noted that cases worldwide appeared to correlate with epidemics of influenza, lethargic encephalitis, and poliomyelitis (Cottom 1957). They were marked by onset predominantly in toddlers, acute onset of symptoms, and overall good prognosis. In 1958, a series of 9 patients with cerebellar ataxia was published, and the etiology was not able to be obtained in any of the children (King et al 1958). The most common presenting sign was ataxic gait; however, truncal ataxia, action tremor, and dysmetria were also frequently seen. Four of the patients had optic nerve changes suggesting increased intracranial pressure, and in 2 cases lumbar puncture demonstrated increased pressure (28 and 24 cm of water). However, 5 of the patients underwent ventricular tap, but intraventricular pressure was not elevated in any of them.

Weiss and Carter reexamined 18 of 23 patients previously reported in the literature to provide information on the course and prognosis of acute cerebellar ataxia in children (Weiss and Carter 1959). Selection criteria included acute onset of neurologic symptoms, signs of cerebellar dysfunction, absence of recent exanthem or exposure to such illnesses, and lack of familial skeletal or neurologic disease. The patients were divided into 2 groups: group 1, in which symptoms resolved within 6 months, and group 2, in which symptoms lasted longer. The common initial presentation for all patients was deterioration of gait, followed in frequency by tremors and then extraocular movement abnormalities. The children in group 1 not only demonstrated resolution of their neurologic symptoms at follow-up, but also did not have any other sequelae noted. In contrast, those in group 2 demonstrated residual neurologic symptoms along with speech and intellectual impairments. The only prognostic indicator noted was that more severe cerebellar dysfunction at onset portended a worse outcome.

In 1994, Connolly and colleagues published the largest series of patients with acute cerebellar ataxia to date, in which they described 73 consecutive patients over a 23-year period (Connolly et al 1994). Unlike some prior and subsequent studies, they excluded patients with altered mental status or seizures, arguing that the original description by Batten in 1905 was of children with acute ataxia and normal mentation. In fact, they pointed out that the definition of acute cerebellar ataxia was still poorly defined; there were no diagnostic criteria, treatment recommendations, or good data on outcome that could be reliably used.

This has continued to be a problem, and even today this condition remains poorly understood and not well delineated. Certainly, 1 of the confusions is whether acute cerebellar ataxia, in which there is typically no alteration in consciousness, and acute cerebellitis, which is often associated with encephalopathy, are in fact 2 separate conditions. Different case series excluded or included patients with altered mental status, rash (as would be expected with varicella), and preexisting developmental delay. Additionally, there have been significant changes in types and availability of brain imaging, as well as increased rates of vaccination for infections such as varicella, polio, influenza, and others; thus, interpretation of many of these older studies is difficult at best. Recent available data will be reviewed later in this article.

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