Paediatric Acute Ataxia

Take-home messages

• Most common causes of acute cerebellar ataxia are post-infectious, drugs (esp. anticonvulsants) and posterior fossa tumours
• Red flags for brain tumour:
• PseudoHeadache, vomiting, papilloedema, cranial nerve dysfunction and behavioural changes
• Ataxia due to weakness should be sought out

Causes

• Cerebellar dysfunction
• Peripheral neuropathy (esp. proprioception)
• Cortical ataxia (esp. frontal lobe)
• Vestibular ataxia
• Hereditary conditions: Friedrich’s ataxia, hereditary cerebellar ataxia, spinocerebellar ataxia and ataxia telangiectasia (all progressive and have associated signs)

Pathophysiology

• Archaecerebellum
  • Flocculus + nodule and lingula of vermis
  • Only vestibular connections via inferior cerebellar peduncle
  • Controls balance
  • Dysfunction
    • Truncal ataxia with swaying and titubation
    • Typically no alteration to fine movements or nystagmus
    • Reflexes are normal and no tremor
• Palaeocerebellum
  • Anterior lobes of lateral hemispheres + uvula and pyramid of vermis
  • Connects to spinocerebellar tracts and controls postural reflexes
  • Dysfunction leads to postural imbalance and hyperreflexia
• Neocerebellum
  • Posterior lobes of lateral hemispheres
  • Connects to cerebral hemispheres, basal nuclei and pontine nuclei via the middle cerebellar peduncle
  • Coordinates fine, voluntary movements
  • Dysfunction leads to nystagmus, intention tremor, dysdiadochokinesis, hypotonia and decreased reflexes

Differential

• Post-viral acute cerebellar ataxia
• Drug intoxication
• Tumours
• Paraneoplastic syndrome
• Trauma including NAI
• Metabolic – Hypoglycaemia, hyponatraemia, hyperammonaemia, inborn errors
• Infections – Meningitis, cerebral abscess, malaria, labyrinthitis, encephalitis
• Vascular – stroke, vasculitis
• Immune – MS, acute disseminated encephalomyelitis (ADEM)

Acute cerebellar ataxia

• Most common cause in children, particularly between ages 2-7
• Diagnosis of exclusion
• Likely autoimmune following varicella, EBV, mycoplasma and human parvovirus B19 (+ coxsackie A9, Mumps, Polio, typhoid, echovirus, pertussis, measles, enterovirus 71, malaria, HHV-6)
• Usually 5-10 days following non-specific illness

• Presentation
  • Sudden onset severe gait ataxia, dysarthric speech, horizontal nystagmus (50%)
  • Intention tremor, dysdiadochokinesis, hypotonia and decreased reflexes in 23 of cases
  • Truncal ataxia is uncommon
  • No focal neurological signs (unlike ADEM and MS)
• Investigations
  • CT normal
  • MRI may show inflammatory changes of the cerebellum
  • May be slight leukocytosis and elevated protein in CSF
• Prognosis
  • Usually improves within days but full recovery can take up to 2 months
  • 91% recover fully
  • Varicella-associated ataxia recovers quicker

Poisoning

• Most often accidental overdose of anticonvulsants (phenytoin, carbamazepine)
• Also can include alcohols, substances of abuse, essential oils, cough suppressants
• May present with ataxia, nystagmus, altered mental status and vomiting
  • Unlike acute cerebellar ataxia where consciousness is not impaired

• Phenytoin
  • Levels >20-30mcg/mL can cause ataxia, nystagmus on lateral gaze and drowsiness
  • Symptom onset usually within 1-2 hours of ingestion and persist for 4-5 days
  • >30mcg/mL may cause more marked loss of consciousness and vertical nystagmus
• Carbamazepine
  • High risk of coma and seizures if >100micromol/L

• Benzodiazepines
  • Ataxia may be the sole presenting feature
  • Lethargy, reduced LOC and respiratory depression
• Alcohols
  • Ethanol intoxication
  • Ethylene glycol
    • Similar presentation to ethanol but delayed cardiopulmonary distress and nephrotoxicity
    • Raised anion gap metabolic acidosis with raised osmolal gap
  • Isopropanol (rubbing alcohol)
    • Vomiting, ataxia, nystagmus, altered LOC, coma and apnoea

• Essential oils
  • Eucalyptus oil
    • Decreased LOC, vomiting, ataxia, respiratory distress
    • >5mL of 100% oil associated with significantly reduced LOC
    • <2-3mL of 100% oil associated with minor depression of LOC
  • Tea tree oil
  • Pine oil
• Codeine
  • Ataxia (9%), somnolence (67%), rash, miosis, vomiting, itching, angioedema
• Dextromethorphan
  • Acts via opioid receptors in medulla
  • Opisthotonus, ataxia and bidirectional nystagmus
  • Fatality very rare (even with doses 100x therapeutic)

• PCP
• LSD
• Hydrocarbons

Tumours

• May present acutely if haemorrhage or obstructive hydrocephalus arise
• Paraneoplastic syndromes are rare in children
  • Paraneoplastic cerebellar degeneration
  • Opsoclonus-myoclonus-ataxia syndrome (occult neuroblastoma)

• Posterior fossa tumours
  • Medulloblastoma (20-25% of posterior fossa tumours)
    • Usually child <6yo with truncal ataxia, headache, irritability or vomiting
  • Cerebellar astrocytoma (10-30% of paediatric brain tumours)
    • Occur in single hemisphere
    • Seen in primary school age with ipsilateral limb ataxia, headache and vomiting
    • Head may be tilted to one side
  • Ependymoma
    • 8-10%
    • Located in 4^th ventricle and can cause obstructive hydrocephalus
    • Headache, vomiting, truncal ataxia
  • Brainstem gliomas
    • 10-15% of paediatric brain tumours
    • Medulla or pons in early primary school age children
    • Cranial nerve palsies, ataxia and vomiting

• Hydrocephalus
  • May present with ataxia due to stretching of frontopontocerebellar fibres
  • Supratentoral tumours can also stretch these fibres
• Occult neuroblastoma
  • Triad of acute ataxia, opsoclonus (jerky, chaotic eye movements) and myoclonus (severe myoclonic jerks of head/trunk/limbs)
  • Usually in abdomen
  • Triad may also be seen in meningitis and mumps so consider LP
  • Always consider neuroblastoma in cases of persistent or recurrent isoalted ataxia

Trauma

• Ataxia can be part of post-concussive syndrome but all should get CT
• Consider NAI in all cases

Infections

• Always consider meningitis/encephalitis
• Labyrinthitis and vestibular neuronitis
  • Vertigo and vomiting are prominent
  • Nystagmus and hearing impairment also features
  • Neurological examination otherwise unremarkable

Pseudo-ataxia

• GBS
  • Areflexia and ophthalmoplegia (miller-fisher variant) distinguish it from acute cerebellar ataxia
• Tick paralysis
• MS/transverse myelitis
  • Usually adolescent age group
• ADEM
  • Post-infectious encephalomyelitis
  • Abnormal CT and MRI
• Seizures (usually recurrent in nature)
  • May be post-ictal or minor motor status or partial complex seizures
  • Other clues include altered LOC and other motor manifestations
• Complex migraine phenomenon
  • Usually recurrent
  • Basilar artery migraine: Headache, blurred vision, visual defects and vertigo

Chronic ataxia

• Hereditary ataxias
  • Friedreich’s ataxia
    • Autosomal recessive condition
    • Child <10 with ataxia and nystagmus
    • Usually rapid progression
    • Impaired position and vibration sense, positive Romberg’s sign and absent tendon reflexes
    • Plantars upgoing
    • Dysarthria is present
    • Kyphoscoliosis, distal muscle wasting, contractures and cardiomyopathy can arise
  • Ataxia telangiectasia
    • Autosomal recessive with neurocutaneous manifestations
    • Truncal ataxia in early childhood
    • Ocular and cutaneous telangiectasia between 2-6 yo
    • Developmental delay, susceptibility to infection (thymic atrophy, IgA and IgE deficiency) and increased incidence of neoplasia are seen

• Congenital malformations
  • Cerebellar aplasia/hypoplasia
  • Dandy-Walker malformations
  • Arnold-Chiari malformations
  • Vermal aplasia
  • Can all cause ataxic cerebral palsy
  • Ataxia, hypotonia, tremor from birth

Clinical presentation

History

• Timing – Acute, recurrent, chronic, progressive?
• Trunk or limbs?
• Associated symptoms – Headache, vomiting, blurred vision, reduced LOC
• Preceding illness
• Possible intoxication
• FHx

Examination

• ABCDE in case of raised ICP, meningitis, head trauma.etc.
• Check BSL
• Full neurological examination, abdominal exam (occult neuroblastoma), skin examination, telangiectasia
• Sensory ataxia differentiated from cerebellar by positive Romberg’s, impaired position and vibration sense
• Cerebellar dysarthria (scanning speech) can be detected by repeated ‘sizzling sausage’ with slow onset, slurred, jerky sound with explosive nature
• Reflexes are crucial (reduced in cerebellar lesions, absent in GBS)

Investigations

• BSL
• Drug levels if indicated
• CT if post-traumatic or signs of raised ICP
• MRI in almost all cases at some point unless clear alternative diagnosis
• LP considered if meningitis/encephalitis/GBS considered (may require preceding CT/MRI)
• Electrolytes, glucose, ammonia + other metabolic screening if suspected

Management

• Aimed at cause
• Admit all patients unless certain post-infectious acute cerebellar ataxia and appropriate outpatient follow-up arranged
• Supportive care

Last Updated on November 10, 2021 by Andrew Crofton