Acute cerebellar ataxia is the most common diagnosis in acute ataxia in children, particularly between 2 and 7 years of age. It is a diagnosis of exclusion, after consideration of more sinister causes such as tumours. An autoimmune aetiology is likely, with autoantibodies demonstrated in acute cerebellar ataxia following infections with varicella,¹^,² Epstein–Barr virus (EBV),³ mycoplasma and human parvovirus B19.⁴ The clinical presentation is of a prodromal illness, frequently non-specific, with or without an exanthema, 5–10 days prior to the onset of acute ataxia, though the timing may show considerable variation. If a specific aetiology is present it is most commonly varicella,⁵ though a number of other viruses have been implicated (Table 8.5.2).⁶^–²² Acute cerebellar ataxia usually presents with sudden onset of severe gait ataxia, though a small number of cases have an insidious onset. Most have dysarthric speech. Mild horizontal nystagmus occurs in 50% of cases. Findings of intention tremor, dysdiadochokinesis, hypotonia and decreased or pendular reflexes are seen in two-thirds of cases, but are less pronounced than the gait disturbance. Truncal ataxia is uncommon. Unlike acute disseminated encephalomyelitis (ADEM) or multiple sclerosis, there are no focal neurological signs.

• Varicella ⁶

• Coxsackie A9 ¹⁰

• Epstein–Barr virus ⁸

• Mycoplasma ⁹

• Mumps ¹⁰

• Poliomyelitis ¹¹^,¹²

• Typhoid ¹³

• Echovirus ¹⁴

• Pertussis ¹⁵

• Human parvovirus ¹⁶

• Measles ¹⁵

• Herpes simplex virus ¹⁷

• Enterovirus 71 ¹⁸

• Malaria ¹⁹

• Immunisation ²⁰^,²¹

• Human herpesvirus-6^,²²

Investigations are aimed at excluding an alternative diagnosis, if the diagnosis is unclear. The computerised tomography (CT) scan is normal in acute cerebellar ataxia; however, magnetic resonance imaging (MRI) may be abnormal. In one series, inflammatory changes were seen in the cerebellum of one of nine children.²³^,²⁴ There is a slight elevation of CSF cell count by 4–50 cells per microlitre in 32%, though occasionally (in 8%) the elevation is higher. There may also be slightly elevated protein 410–900 mg L^–1.²⁵

Acute cerebellar ataxia usually begins to improve within a few days, but full recovery may take from 10 days to 2 months. Patients who have a slower recovery are still likely to recover fully. In one series, 91% recovered fully from their ataxia, including all those with varicella, EBV or post-vaccination, but 8% had sustained learning problems. Varicella-associated ataxia recovered quicker than non-varicella.²⁴

Poisoning

Ataxia is not uncommonly a presenting symptom of ingestion or excessive therapeutic drug levels, particularly anticonvulsants.

Accidental poisoning occurs most commonly in 1 to 4-year-old children. A wide variety of compounds are implicated, including alcohols, substances of abuse and essential oils, as well as medications (Table 8.5.3). In addition to ataxia, these children may have nystagmus, altered mental status and vomiting. This is different to acute cerebellar ataxia where consciousness is unimpaired.

Solvents, petrol, glue

Anticonvulsants

Phenytoin toxicity with serum levels of >20–30 mcg mL^–1 may produce signs of ataxia, nystagmus on lateral gaze and drowsiness. Onset of symptoms following an acute ingestion is usually within 1–2 hours and may persist for 4–5 days. At >30 mcg mL^–1, the ataxia and drowsiness become more marked and the nystagmus vertical.²⁶^–²⁸

Carbamazepine toxicity may also lead to ataxia. There are usually associated findings of drowsiness and nystagmus. There may be progression to seizures and coma, particularly if the level is >100 μmol L^–1.²⁹

Benzodiazepines

Ataxia may be the sole presenting feature of benzodiazepine ingestion in children. In one series, it was an isolated finding in one-fifth of the cases who demonstrated ataxia. Other findings included lethargy (57%), GCS <15 (35%) and respiratory depression (9%).³⁰

Alcohols

Ethanol intoxication produces ataxia, disinhibited behaviour and slurred speech. A serum ethanol level will aid clarification of the diagnosis.

Ethylene glycol is the main component of antifreeze. Early symptoms of ingestion are similar to those of ethanol intoxication. Delayed features include cardiopulmonary distress and nephrotoxicity. Ethylene glycol produces a raised anion gap metabolic acidosis with osmolal gap. Serum levels >20 mg dL^–1 are toxic. The ethanol level will be zero. Isopropanol, a component of rubbing alcohol, is used widely as a solvent. Toxicity is evident between 0.5 and 2 hours post-ingestion and may include vomiting, ataxia, nystagmus, and altered mental state. Coma and apnoea may occur in severe poisoning.³¹

Essential oils

Eucalyptus oil is not an uncommon ingestion by children. In one series of 109 admitted children, 41% were asymptomatic. Those who were symptomatic demonstrated decreased conscious state (28%), vomiting (37%), ataxia (15%) and pulmonary disease (11%). There was a correlation between ingested dose and toxicity. An ingestion of >5 mL 100% oil was associated with a significantly decreased conscious state, whereas <2–3 mL was associated with minor depression of consciousness.³² A second series of 41 presentations, however, only demonstrated effects in 20%, with no correlation with presumed dose. The clinical effects included ataxia (5%), decreased conscious state (10%) and gastrointestinal symptoms (7%).³³

Other essential oils that may produce nystagmus include tea tree oil ³⁴ and pine oil. In one small series of pine oil cleaner (35% pine oil, 10.9% isopropyl alcohol), symptoms developed within 90 minutes of ingestion. Lethargy was present in all symptomatic children and ataxia in four of five cases of children.³⁵

Cough suppressants

Codeine is contained in a number of cough medicines as well as in analgesics. In one series of 430 children, ataxia was reported in 9% receiving codeine. Associated symptoms are somnolence 67%, rash 39%, miosis 30%, vomiting 27%, itching 10%, angio-oedema 9%.³⁶ Dextromethorphan is a common component of cough and cold medications, which acts through opiate receptors in the medulla. It may cause opisthotonus, ataxia and bidirectional nystagmus. Fatality is highly unlikely, even with one hundred-fold the therapeutic dose.³⁷^,³⁸

Substances of abuse

Phencyclidine (PCP) and lysergic acid diethylamide (LSD) are rare causes of ataxia in children. 1,4-butanediol, which is metabolised to gamma-hydroxybutyrate (GHB) upon ingestion, was responsible for ataxia, vomiting and seizures in several children following the ingestion of Aqua Dots, from toy craft kits.³⁹

More common, however, is the abuse of hydrocarbon solvents; toluene in glue, spray paints and petrol. Hydrocarbons may produce ataxia as a component of acute intoxication and also as a chronic central nervous system sequel.

Tumours

Cerebellar lesions may present with an acute, rather than insidious onset of ataxia as a result of either haemorrhage into a tumour or as a result of hydrocephalus. The ataxia may progress to chronic ataxia. Paraneoplastic syndromes including paraneoplastic cerebellar degeneration and opsoclonus-myoclonus-ataxia syndrome are uncommon causes of acute paediatric ataxia.

Clinical features suggestive of a brain tumour, and hence further investigation, include headache, vomiting, behavioural changes (particularly with frontal lobe lesions), papilloedema or cranial nerve dysfunction.

Posterior fossa tumours include medulloblastoma, astrocytoma and ependymoma. Medulloblastoma (20–25% of posterior fossa tumours) usually presents in a child of less than 6 years with symptoms of ataxia, which may be truncal, headache, irritability or vomiting. The tumour may be located in the 4th ventricle or vermis. Cerebellar astrocytoma (10–30% of paediatric brain tumours) is located in one of the cerebellar hemispheres. It is seen in primary-school-aged children who may display ipsilateral limb ataxia, headache and vomiting. The head may be held tilted to one side. Associated raised intracranial pressure may be life threatening. Ependymoma (8–10%), located in the 4th ventricle, causes obstruction of CSF flow and may present with headache, vomiting and ataxia, which may be truncal. Brainstem gliomas (10–15% of paediatric brain tumours) develop in the pons or medulla. They typically occur in early primary-aged children. Presenting symptoms include cranial nerve palsies, ataxia and vomiting.

Hydrocephalus may present with ataxia due to stretching of frontopontocerebellar fibres. Associated features are headache, vomiting and the late signs of raised intracranial pressure – altered conscious state, raised blood pressure and decreased pulse. Supratentorial tumours may also present with ataxia through involvement of the frontopontocerebellar fibres.

An occult neuroblastoma may present with a triad of acute ataxia, opsoclonus (jerky, random, chaotic eye movements) and myoclonus (severe myoclonic jerks of the head, trunk or limbs). The most common site for the tumour is in the abdomen.⁴⁰ The triad may also be seen with viral infections, including meningitis, particularly mumps, hence a lumbar puncture should be considered. Neuroblastoma may present with isolated ataxia and should be considered in cases of persistent or recurrent ataxia.⁴¹

Trauma

Head trauma is a frequent cause of ED presentations. While ataxia may be seen in post-concussion syndrome, intracranial injury requiring acute intervention, should be sought by CT scan. These include haemorrhage or cerebral oedema. A base-of-skull fracture may cause ataxia by direct damage to the vestibular apparatus. Non-accidental injury should be considered in all cases of paediatric trauma.

Infections

Meningitis and encephalitis may both have ataxia as a presenting feature.⁴²^,⁴³ Other features to suggest an infective cause, such as headache, vomiting, fever and neck stiffness in the older child, will usually be evident.

In labyrinthitis and vestibular neuronitis, vertigo and vomiting are prominent. Apart from nystagmus and hearing alterations, neurological examination is normal.