Differentials
Viral gastroenteritis in adults
Transverse myelitis
SIGNS / SYMPTOMS
Usually symmetrical motor and sensory loss below the level of the spinal cord lesion. Approximately one third of patients report a febrile illness preceding the symptoms.
INVESTIGATIONS
MRI usually shows spinal cord inflammation and focal demyelination.[1]
CSF analysis usually shows elevated protein. Viral cultures should be negative for poliovirus.
Guillain-Barre syndrome (GBS)
SIGNS / SYMPTOMS
Similar, in that it may also be preceded by viral syndrome such as gastroenteritis. However, any limb weakness is usually symmetrical, and cranial nerve weakness may be present as well. Other differentiating symptoms include those of autonomic dysfunction, which are not typical of poliomyelitis.
INVESTIGATIONS
Typical CSF findings include albumin-cytological dissociation: an elevated protein level (1 to 10 g/L [100 to 1000 mg/dL or 0.1 to 1 g/dL]) without an accompanying increased cell count. A sustained increased WBC count may indicate an alternative diagnosis such as infection.
Viral cultures should be negative for poliovirus.
Serological and stool testing may show evidence of recent Campylobacter jejuni infection (up to 40% of GBS patients).
Electrodiagnostics (electromyography and nerve conduction studies) may show prolonged distal latencies, conduction slowing, and conduction block.
Encephalitis
SIGNS / SYMPTOMS
Does not usually result in unilateral paralysis and muscle atrophy; may have features not associated with poliomyelitis, such as mental status changes, fevers, and seizures.
Enterovirus D-68
SIGNS / SYMPTOMS
Usually causes a mild to severe respiratory, rather than gastrointestinal, illness.
INVESTIGATIONS
As a non-polio enterovirus, diagnosis by PCR can be done at specialised centres in the case of severe illness needing laboratory confirmation.
Leprosy
SIGNS / SYMPTOMS
Chronic infectious disease affecting children and young adults in endemic areas; involves peripheral nerves, resulting in loss of sensation, weakness, and muscle wasting.
Nerve thickening and skin lesions distinguish leprosy from poliomyelitis.
INVESTIGATIONS
Skin scraping, skin or nerve biopsy, and histopathology show granulomas and acid-fast bacilli (AFBs).
Tetanus infection
SIGNS / SYMPTOMS
History of wound infection. Non-immunised and immunosuppressed children and adults are most susceptible.
Life-threatening neurological symptoms include muscle spasms, restlessness, irritability, dysphagia, opisthotonus, and seizures, as well as respiratory failure due to powerful contraction of the intercostal muscles or involvement of the glottis or diaphragm. Severe autonomic dysfunction may arise after several days.
INVESTIGATIONS
Caused by the exotoxin of Clostridium tetani, a gram-positive, spore-forming obligate anaerobic bacillus. The spores of the organism may be detected within the wound.
Tetanus toxin can be detected in serum, confirming a clinical diagnosis. Samples must be collected prior to immunoglobulin treatment. Absence of toxin in the serum does not exclude the clinical diagnosis.
Rabies
SIGNS / SYMPTOMS
There is usually a history of animal bite, but as the incubation period may be several months, the history may be unclear. Symptoms begin with fever, malaise, and headache, and then progress to seizures, inability to swallow (water), and coma. Death is from respiratory insufficiency.
INVESTIGATIONS
Rabies is a viral zoonotic infection that causes encephalitis in mammals. The virus travels from the peripheral nervous system.
Rabies infection is diagnosed by performing PCR or viral culture on skin samples taken before death, or on brain samples taken after death. It is also possible to make the diagnosis from saliva, urine, and CSF samples, but this is not as sensitive.
Inclusion bodies called Negri bodies may be found in infected tissues on histopathology.
Botulism
SIGNS / SYMPTOMS
Toxin ingestion, usually from contaminated food, leads to a clinical syndrome characterised by cranial nerve palsies, oculobulbar weakness, and descending, symmetrical flaccid paralysis in the absence of fever. Affected patients do not complain of sensory deficits. Children are most susceptible.
Descending symmetrical paralysis affects the voluntary muscles of the neck, shoulders, and upper extremities, followed by the proximal and distal lower extremities.
INVESTIGATIONS
Caused by the exotoxin of Clostridium botulinum, a large, gram-positive anaerobic bacillus. The toxin may be identified in serum, stool, and gastric samples, or in contaminated food.
Aseptic meningitis
SIGNS / SYMPTOMS
Headache, neck stiffness, and fever with no altered mental status (maybe mild somnolence) and focal neurological signs.
Frequently meningitis and encephalitis co-exist.
May be difficult to distinguish from non-paralytic poliovirus infection.
INVESTIGATIONS
MRI shows evidence of meningeal enhancement, with no evidence of brain parenchymal involvement.
HIV-related myelopathy
SIGNS / SYMPTOMS
Signs and symptoms referable to the spinal cord lesions, including paraparesis, often accompanied by spasticity or ataxia (or both) coupled with dementia.
INVESTIGATIONS
ELISA testing should be ordered when HIV testing is indicated. False negatives may occur during a window period immediately after infection and before antibodies to HIV have developed. A positive result should be confirmed with a Western blot or a second ELISA. The window period can be reduced to 2 to 4 weeks by using fourth-generation tests and those that include IgM antibodies to HIV.
CSF, microbiological, and spinal imaging studies are inconclusive or unspecific.
Amyotrophic lateral sclerosis (ALS)
SIGNS / SYMPTOMS
Approximately 60% of ALS patients experience muscle weakness and stiffness as the initial symptom. Examination also reveals muscle atrophy and rigidity. Peripheral hyper-reflexia is often present, which is not typical for poliomyelitis.
INVESTIGATIONS
Electromyography (EMG) testing is a significant part of the diagnosis of ALS. The current criteria define a positive EMG when signs of active denervation include fibrillation potentials and positive sharp waves, with fasciculation potentials.
Multiple sclerosis
SIGNS / SYMPTOMS
Neurological manifestations of poliomyelitis can mimic clinical symptoms of multiple sclerosis, but in almost all cases of multiple sclerosis there are also brain lesions.
Multiple sclerosis has a more variable presentation, with multiple episodes separated by space (i.e., neurological symptoms result from lesions in different CNS sites) and time. Symptoms may include progressive limb weakness, gait difficulty, ataxia, loss of balance, paroxysmal vertigo.
INVESTIGATIONS
Brain MRI typically shows areas of demyelination.
CSF examination shows raised IgG and oligoclonal banding.
Peripheral neuropathy
SIGNS / SYMPTOMS
Compression neuropathies and neuropathies due to metabolic disease, drugs, or toxins may be difficult to differentiate from neurological symptoms of poliomyelitis.
INVESTIGATIONS
Nerve conduction studies and EMG are helpful in confirming neuropathy and characterising the neuropathy (i.e., demyelinating, axonal, polyneuropathy, mononeuropathy multiplex, radiculopathy, or plexopathy).
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