Acute Flaccid Paralysis Approach
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Direct answer
Acute flaccid paralysis is an abrupt onset of limb weakness with reduced tone and reflexes, and in India it is screened as a surveillance case in children under 15 years. The approach is to exclude poliomyelitis first, then separate Guillain-Barré syndrome, transverse myelitis, periodic paralysis and botulism by pattern, sensation, cerebrospinal fluid and electrolytes. Every case is notified, and stool samples are collected to confirm or exclude polio.
What you must remember
- Definition: an acute onset of flaccid weakness with reduced or absent reflexes; in surveillance terms the case is a child under 15 years.
- Poliomyelitis: asymmetric weakness, often in the legs, after a febrile prodrome, with sensation classically spared and possible bulbar or respiratory involvement.
- Guillain-Barré syndrome: symmetric ascending weakness with areflexia, often following a diarrhoeal illness such as Campylobacter jejuni infection or a viral infection.
- Transverse myelitis: a sensory level, with bladder and bowel involvement, and a cord lesion on spinal MRI.
- Periodic paralysis: episodic weakness with low potassium; thyrotoxic periodic paralysis is classically seen in young men of Asian origin.
- Botulism: descending weakness with cranial nerve involvement, dilated pupils and autonomic features.
- Surveillance target: a non-polio AFP rate of at least 2 per 100,000 children under 15 years indicates sensitive surveillance.
A pattern-first differential workup
A 4-year-old boy wakes with weakness of the right leg after a mild fever two days earlier. The approach narrows the differential by pattern before any test is sent.
- Confirm the flaccid pattern: check tone, reflexes, sensation, cranial nerves and bladder function to separate peripheral from central causes.
- Check the distribution: asymmetric leg weakness after fever favours polio, symmetric ascending weakness favours Guillain-Barré syndrome, and a sensory level with bladder involvement favours myelitis.
- Notify and collect stool: report the case promptly and collect two stool samples at least 24 hours apart within 14 days of onset for poliovirus testing.
- Examine the cerebrospinal fluid: early polio may show pleocytosis, while Guillain-Barré syndrome shows raised protein with a normal cell count after the first week.
- Test electrolytes and thyroid function: low potassium with episodic weakness suggests periodic paralysis, and thyroid function tests look for thyrotoxicosis.
- Image and monitor: MRI of the spine assesses transverse myelitis, while breathing and swallowing are watched closely in polio and Guillain-Barré syndrome because respiratory failure can develop quickly.
High-yield viva angles
Viva questions usually turn on pattern and sensation rather than on the paralysis itself.
- Trap: labelling every acute flaccid paralysis in a child as Guillain-Barré syndrome Correct: polio is excluded first, because it is notifiable and the stool test is part of the surveillance duty.
- Trap: expecting sensory loss in polio Correct: polio classically spares sensation, whereas Guillain-Barré syndrome and transverse myelitis may show sensory symptoms or signs.
- Trap: accepting a normal early CSF protein as excluding Guillain-Barré syndrome Correct: albuminocytologic dissociation appears only after the first week, so an early lumbar puncture can be normal and nerve conduction studies help.
Frequently asked questions
Which investigation confirms poliomyelitis in acute flaccid paralysis?
Poliovirus is confirmed by isolating the virus from stool in a WHO-accredited polio laboratory. Two stool samples, at least 24 hours apart and within 14 days of onset, are collected from every case. Two adequate samples are the surveillance standard.
How does Guillain-Barré syndrome differ from poliomyelitis in a child?
Guillain-Barré syndrome usually produces symmetric ascending weakness with areflexia, often after a diarrhoeal or viral illness. Poliomyelitis is typically asymmetric and may follow a febrile prodrome, with sensation commonly spared. Nerve conduction studies and cerebrospinal fluid protein help separate the two.
What is the cerebrospinal fluid pattern in Guillain-Barré syndrome?
Guillain-Barré syndrome typically shows albuminocytologic dissociation, meaning raised cerebrospinal fluid protein with a normal white cell count. This pattern usually appears after the first week of illness, so an early lumbar puncture may be normal. Repeat assessment or nerve studies are used when the early result is unclear.
How is periodic paralysis from low potassium managed?
Hypokalaemic periodic paralysis is managed by correcting potassium cautiously, with cardiac monitoring during replacement. Thyrotoxic periodic paralysis is treated by controlling the thyrotoxicosis and correcting potassium, with beta blockers used to control symptoms.