Paediatrics chapters
Coma and cerebellar ataxia in children
How to assess and manage a comatose child, from first steps and the Glasgow Coma Scale to breathing patterns, pupils and posture; and the causes and approach to ataxia, including acute post-infectious cerebellar ataxia.
- Coma is unrousable unresponsiveness from dysfunction of both cerebral hemispheres or the brainstem; in children the common causes are infection (meningitis, encephalitis, cerebral malaria), metabolic (hypoglycaemia, DKA, hepatic, uraemia), toxins, trauma, hypoxia and postictal states.
- Secure airway, breathing, circulation and check glucose first; then use the Glasgow Coma Scale (3-15), breathing pattern, pupils, eye movements and posture to localise; CT before lumbar puncture if raised ICP is suspected.
- Ataxia is clumsy, uncoordinated movement from cerebellar dysfunction; the commonest acute causes are drug intoxication and post-infectious acute cerebellar ataxia (often after varicella, age 2-6, recovers in weeks); progressive ataxia with headache suggests a posterior fossa tumour.
On this page
Overview
Coma is a state of unresponsiveness from which the child cannot be roused, even by painful stimuli. It is a sign of brain dysfunction, not a diagnosis. Consciousness depends on the cerebral cortex and on arousal from the reticular activating system in the brainstem, so coma means both hemispheres, the brainstem, or both are affected. Ataxia is the inability to make smooth, accurate, coordinated movements, usually from a problem in the cerebellum or its pathways. Both are common exam scenarios.
Part 1: Coma
Levels of consciousness (Nelson)
| Level | Description |
|---|---|
| Lethargy | Hard to keep awake |
| Obtundation | Reduced alertness but responds to stimuli |
| Stupor | Responds only to pain |
| Coma | No response, unrousable |
Causes
| Group | Examples |
|---|---|
| Infection | Meningitis (pyogenic, tuberculous), encephalitis (herpes simplex), cerebral malaria, brain abscess, sepsis |
| Metabolic | Hypoglycaemia, diabetic ketoacidosis, hepatic encephalopathy, Reye syndrome, uraemia, sodium disturbance, hypoxia, hypercapnia, inborn errors, hyperammonaemia |
| Toxins | Opiates, barbiturates, benzodiazepines, aspirin, iron, antihistamines, anticonvulsants, alcohol, organophosphates, lead, carbon monoxide |
| Trauma | Subdural and extradural haematoma, concussion, shaken baby syndrome |
| Hypoxia-ischaemia | Near-drowning, cardiac arrest, shock, strangulation |
| Seizures | Postictal state, non-convulsive status epilepticus |
| Structural and vascular | Tumours, hydrocephalus (including shunt block), stroke, haemorrhage |
| Others | Hypertensive encephalopathy, heat stroke, intussusception in infants |
Nelson: the commonest causes of coma in childhood are toxins, infections, head trauma, hypoxia-ischaemia and seizures.
Immediate management (before the full history)
- Airway: clear, suction, side (semi-prone) position to prevent aspiration; intubate if the airway cannot be kept safe.
- Breathing: oxygen, pulse oximetry.
- Circulation: treat shock with fluids; stop bleeding.
- Glucose: check at once; give IV dextrose if low (hypoglycaemia is the quickest reversible cause).
- Stop seizures, control temperature, protect the cervical spine if trauma is possible.
Hypoxia is the commonest cause of lasting damage in a comatose child, so ABC comes first, then glucose.
History
Speed of onset (sudden in trauma, bleeding or poisoning; gradual in metabolic disease, tumour or tuberculous meningitis), fever, headache, vomiting, convulsions, jaundice, drug or poison access, head trauma, heat exposure, and chronic illness (diabetes, kidney or liver failure, bleeding disorder, heart disease).
Glasgow Coma Scale
| Response | Older child | Infant (pre-verbal) | Score |
|---|---|---|---|
| Eye opening | Spontaneous | Spontaneous | 4 |
| To voice | To voice or sound | 3 | |
| To pain | To pain | 2 | |
| None | None | 1 | |
| Best verbal | Oriented | Smiles, coos, follows | 5 |
| Confused | Cries but consolable | 4 | |
| Inappropriate words | Persistent inappropriate crying or screaming | 3 | |
| Incomprehensible sounds | Grunts, agitated, restless | 2 | |
| None | None | 1 | |
| Best motor | Obeys commands | Normal spontaneous movement | 6 |
| Localises pain | Localises pain | 5 | |
| Withdraws from pain | Withdraws from pain | 4 | |
| Abnormal flexion (decorticate) | Abnormal flexion | 3 | |
| Extension (decerebrate) | Extension | 2 | |
| None | None | 1 |
- Total 3 to 15. Head injury severity: mild 13-15, moderate 9-12, severe 8 or less.
A 6-year-old opens eyes only to pain (E2), makes incomprehensible sounds (V2) and withdraws from a painful stimulus (M4).
GCS = 2 + 2 + 4 = 8 → severe
Clues on examination
Vital signs
| Finding | Suggests |
|---|---|
| Fever | Infection, heat stroke |
| Hypothermia | Shock, intoxication (sedatives, alcohol) |
| Slow breathing | Opiate or sedative poisoning, central respiratory failure |
| Deep sighing (Kussmaul) breathing | Metabolic acidosis: DKA, uraemia, salicylate poisoning |
| Cheyne-Stokes breathing (waxing and waning with apnoea) | Bilateral cortical or diencephalic dysfunction, metabolic disease |
| Central neurogenic hyperventilation | Midbrain lesion |
| Ataxic or gasping breathing | Lower brainstem (medulla) damage; often precedes apnoea |
| Bradycardia with hypertension | Raised ICP (Cushing response) |
| Hypertension alone | Hypertensive encephalopathy |
Skin and breath: pallor (bleeding), cyanosis, petechial or purpuric rash (meningococcus, endocarditis), dehydration, sweating (hypoglycaemia, shock), dry hot skin (heat stroke), fruity breath (DKA), uraemic smell, mousy smell (hepatic coma), jaundice, needle marks, injuries.
Pupils
| Pupils | Meaning |
|---|---|
| Small, reactive | Metabolic coma |
| Pinpoint | Opiates, organophosphates, phenothiazines, pontine lesion |
| Mid-position, fixed | Midbrain damage |
| One dilated, unreactive | Third nerve compression from uncal (tentorial) herniation |
| Both dilated | Postictal state, atropine-like drugs |
Reactive pupils in deep coma suggest a metabolic or toxic cause; a unilateral fixed dilated pupil is a neurosurgical emergency.
Eye movements
- Doll's eye (oculocephalic) reflex: turn the head; if the brainstem is intact, the eyes move opposite to the head (keep looking at the same point). Absent if the brainstem is damaged. Avoid if neck injury is possible.
- Cold caloric test: in coma with an intact brainstem, cold water in the ear causes the eyes to deviate towards that ear.
- Sixth nerve palsy (convergent squint) is a non-localising sign of raised ICP.
Posture
| Posture | Description | Level |
|---|---|---|
| Decorticate | Arms flexed, legs extended | Cortex or subcortical lesion; brainstem working |
| Decerebrate | Arms and legs extended, arms internally rotated | Midbrain/upper brainstem; herniation or severe metabolic disease |
| Flaccid, no response | — | Lower brainstem failure |
Meningeal signs (meningitis, subarachnoid haemorrhage), fundi (papilloedema in raised ICP; retinal haemorrhages in subarachnoid bleeding, hypertension and cerebral malaria) and lateralising signs (hemiplegia).
"De-COR-ticate = arms to the COR (heart), flexed; deCEREbrate = everything straight, deeper damage."
Raised ICP and herniation
- Signs: headache, vomiting, papilloedema, third or sixth nerve palsy, falling consciousness, Cushing triad (hypertension, bradycardia, irregular breathing) as a late sign.
- Uncal herniation: dilated pupil on one side, third nerve palsy, hemiparesis, decerebrate posture.
- Tonsillar (foramen magnum) herniation: bradycardia, slow breathing, hypertension, apnoea and death.
- Emergency treatment: head up 30 degrees, midline, intubation with controlled ventilation, mannitol or hypertonic saline, treat the cause.
Kussmaul breathing means metabolic acidosis (DKA, uraemia, salicylates); slow shallow breathing suggests opiates or sedatives.
Decerebrate posture indicates a deeper (midbrain or brainstem) lesion than decorticate posture.
Investigations
- Glucose, electrolytes, urea, creatinine, calcium, blood gases, ammonia, liver tests, blood count and culture.
- Toxicology screen; malaria film where relevant; lead level if suspected.
- CT head (without contrast first) in trauma, focal signs or suspected raised ICP; MRI for detail.
- Lumbar puncture: infection must be considered in every comatose child, but the LP is done only after raised ICP and mass lesions are excluded; give antibiotics first if needed.
- EEG to detect non-convulsive status or encephalitis.
Ongoing care
Nurse on the side, frequent suction, turn regularly against pressure sores, eye and mouth care, bladder catheter if retention, bowel care, nasogastric feeding when stable, physiotherapy against contractures, prevent falls, and never leave the child unattended.
Prognosis
Depends on the cause: hypoxic-ischaemic coma has a poor outlook, while toxic and metabolic coma often recover fully if treated early. Once both pupils are fixed and dilated with absent eye movements and flaccid limbs after herniation, recovery is not possible (Nelson).
Part 2: Ataxia
Definition and signs
Ataxia is the inability to make smooth, accurate and coordinated movements, usually from cerebellar dysfunction.
- Truncal ataxia: broad-based, unsteady gait, falls; from midline vermis lesions (medulloblastoma, acute cerebellar ataxia).
- Limb (appendicular) ataxia: intention tremor and dysmetria (over- or undershooting a target), on the same side as a cerebellar hemisphere lesion.
- Others: nystagmus, dysarthria (slurred speech), hypotonia.
- Sensory ataxia (loss of joint position sense, for example Guillain-Barré syndrome) can mimic it; weakness can also look like ataxia, so test strength.
Causes
| Group | Examples |
|---|---|
| Toxic (commonest acute) | Anticonvulsants (phenytoin, carbamazepine, phenobarbitone), benzodiazepines, antihistamines, alcohol, lead |
| Post-infectious | Acute cerebellar ataxia (after varicella), ADEM, Guillain-Barré syndrome |
| Infection | Encephalitis, meningitis, cerebellar abscess, labyrinthitis |
| Tumours | Posterior fossa: medulloblastoma, cerebellar astrocytoma, ependymoma, brainstem glioma; neuroblastoma (opsoclonus-myoclonus) |
| Others | Head trauma, basilar migraine, benign paroxysmal vertigo, postictal state, stroke, hydrocephalus |
| Congenital, structural | Ataxic cerebral palsy, Dandy-Walker, Chiari malformation, cerebellar hypoplasia |
| Inherited and metabolic | Ataxia-telangiectasia, Friedreich ataxia, Wilson disease, leukodystrophies, maple syrup urine disease, Hartnup disease, vitamin E deficiency, abetalipoproteinaemia |
Acute post-infectious cerebellar ataxia
- Commonest at 2-6 years (Akbar).
- Starts suddenly 1-3 weeks after a viral illness, especially varicella, also infectious mononucleosis and respiratory or gut viruses.
- Truncal ataxia with staggering and falls, often unable to stand or sit; also nystagmus, dysarthria, dysmetria, vomiting and irritability.
- No fever, no neck stiffness, no raised ICP, normal consciousness, normal sensation and reflexes.
- CSF normal or a mild lymphocytosis; CT normal; MRI may show cerebellar changes.
- Thought to be immune-mediated. Treatment is supportive (prevent injury); symptoms peak within days and recover fully over weeks (Akbar: within about 6-8 weeks).
Before calling it post-infectious ataxia, exclude drug ingestion (the commonest acute cause), posterior fossa tumour (progressive, headache, raised ICP) and cerebellar abscess or encephalitis (fever, drowsiness).
Posterior fossa tumours
Brain tumours are the second commonest childhood malignancy after leukaemia, and about half arise in the posterior fossa. They cause progressive ataxia with headache and vomiting over days to months, often with hydrocephalus. CT or MRI is mandatory; lumbar puncture is contraindicated until a mass is excluded.
Opsoclonus-myoclonus
Chaotic darting eye movements (opsoclonus), myoclonic jerks, ataxia and irritability: an immune reaction to a hidden neuroblastoma, which must be searched for.
Inherited ataxias
| Disorder | Key facts |
|---|---|
| Ataxia-telangiectasia | Autosomal recessive; the commonest degenerative ataxia; ataxia from about 2 years, loss of walking by adolescence; telangiectasia of conjunctivae, ears and nose in mid-childhood; immune deficiency with infections and lymphoreticular malignancy |
| Friedreich ataxia | Autosomal recessive, progressive from school age; ataxia, dysarthria, absent tendon reflexes, loss of position and vibration sense, nystagmus; hypertrophic cardiomyopathy, pes cavus, scoliosis |
Expect: common causes of coma (infection, metabolic, toxins, trauma, hypoxia, seizures); ABC and glucose first; GCS scoring and severe at 8 or less; breathing patterns (Kussmaul, Cheyne-Stokes); pupils (pinpoint in opiates and organophosphates, unilateral dilated in uncal herniation); decorticate versus decerebrate posture; doll's eye reflex; CT before LP when ICP is raised; acute cerebellar ataxia after varicella in a well afebrile toddler with full recovery; drug intoxication as the commonest acute cause; posterior fossa tumour with progressive ataxia and headache; ataxia-telangiectasia and Friedreich ataxia features; opsoclonus-myoclonus and neuroblastoma.
Quick revision
- Coma: unrousable; bilateral hemisphere or brainstem dysfunction.
- Causes: infection, metabolic, toxins, trauma, hypoxia, seizures, structural.
- ABC, then glucose, then GCS and localisation.
- GCS 3-15; severe 8 or less.
- Decorticate (arms flexed) above brainstem; decerebrate (all extended) brainstem.
- Pinpoint pupils: opiates, organophosphates, pons; one fixed dilated pupil: uncal herniation.
- CT before LP if raised ICP suspected.
- Ataxia: commonest acute causes are drugs and post-varicella cerebellar ataxia (recovers in weeks).
- Progressive ataxia with headache: posterior fossa tumour.
- A-T: telangiectasia, immune deficiency; Friedreich: areflexia, cardiomyopathy, pes cavus.
Written by The House Job from standard references (Basis of Paediatrics by Pervez Akbar; Nelson Essentials of Paediatrics).
FAQ
What should be done first for a comatose child?
Secure the airway, breathing and circulation, then check the blood glucose and correct hypoglycaemia. History, examination and tests follow once the child is stable.
What GCS score means severe brain injury?
A score of 8 or less. These children need intensive monitoring and close attention to the airway.
How do decorticate and decerebrate postures differ?
Decorticate posture has flexed arms and extended legs and indicates a lesion above the brainstem. Decerebrate posture has all limbs extended and indicates midbrain or brainstem dysfunction, a more serious sign.
A child becomes unsteady two weeks after chickenpox. Is this serious?
It is usually acute post-infectious cerebellar ataxia, which resolves over a few weeks with supportive care. Drug ingestion, a posterior fossa tumour and infection should be excluded first.