Aug. 11, 2022
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Acute cerebellar ataxia is a relatively common disorder among children, usually observed following an acute viral illness or vaccination. The typical 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.
• 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 have been reported, such as Epstein-Barr virus, influenza, and Mycoplasma.
• More than 90% of children recover, and treatment is typically supportive.
• Acute cerebellitis is a severe subtype of acute cerebellar ataxia that includes MRI changes that may be confused with tumors.
• Cerebellar swelling can result in fatal or near-fatal outcome, and prompt recognition and treatment is essential in these cases.
In 1905, Batten published a seminal article on ataxia in children in which he subdivided ataxia into three 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” (05). 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 and 1921 reporting the clinical findings of four of his patients and summarizing the literature to date for an additional 27 patients (34). 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 eight cases, influenza in five cases, and typhoid fever in four 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 (25). In 1957, Cottom published a series of seven cases of acute cerebellar ataxia, and in reviewing the cases previously reported in the literature, noted that cases worldwide appeared to correlate with epidemics of influenza, lethargic encephalitis, and poliomyelitis (16). They were marked by onset predominantly in toddlers, acute onset of symptoms, and overall good prognosis. In 1958, a series of nine patients with cerebellar ataxia was published, and the etiology was not able to be obtained in any of the children (48). 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 two cases lumbar puncture demonstrated increased pressure (28 and 24 cm of water). However, five 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 (93). 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 two 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 addition, one third of non-varicella-related acute cerebellar ataxia were present in group 2 with residual neurologic deficits.
In order to help clarify the variable outcomes documented in children with cerebellar ataxia, 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 (15). Unlike other 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. Their study found that when rigorous exclusion criteria were implements, children with acute cerebellar ataxia were clinically uniform with prominent gait ataxia (due to truncal and lower extremity involvement). Two thirds of these children had other signs of hemispheric dysfunction, particularly dysmetria and fine motor impairment. Greater than 4-month follow-up in this cohort revealed full recovery in 91% of patients. Persistence of symptoms beyond 6 months did not portend a poorer outcome either. They did, however, note that a significant portion of patients on follow-up had higher cortical dysfunction.
With the advent of MRI imaging, the term acute cerebellitis is now defined as “an acute neurologic condition characterized by cerebellar ataxia or dysfunction that is attributable to recent or concurrent infective illness, a recent vaccination, or ingestion of medication, and in which there is MRI evidence of predominantly cerebellar inflammation” (26). Some authors feel that acute cerebellitis and acute postinfectious cerebellar ataxia are in fact a spectrum of the same disease (51). Imaging findings in acute cerebellitis have been categorized as bihemispheric acute cerebellitis, hemicerebellitis, or acute cerebellitis with encephalitis. The inflammation seen in these patients can result in increased intracranial pressure, requiring a medical or neurosurgical intervention to prevent death. Patients may also have additional symptoms of headache, vomiting, and altered consciousness (96). Despite acute cerebellitis being a more severe clinical course than acute cerebellar ataxia, the majority of patients do recover.
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