Myalgic Encephalomyelitis (also known as Enteroviral Encephalomyelitis), Enteroviral Poliomyelitis-like Syndrome (with asymmetrical Flaccid Weakness or Flaccid Paralysis) and Enteroviral Encephalitis (Meningoencephalitis, Limbic Encephalitis and Rhombencephalitis)

Overview

Enteroviral encephalomyelitis, enteroviral poliomyelitis-like syndrome and enteroviral encephalitis are neurological conditions caused by infection with enteroviruses (a group of viruses that includes coxsackieviruses, echoviruses and numbered enteroviruses such as EV-A71 and EV-D68).

These conditions affect the central nervous system (CNS) and may involve:

The brain (encephalitis)

The spinal cord (myelitis)

Both brain and spinal cord (encephalomyelitis)

The anterior horn cells of the spinal cord (poliomyelitis-like syndrome), which control muscle movement

They are part of a spectrum of enteroviral CNS disease, rather than completely separate illnesses.

How they differ?

Enteroviral encephalitis mainly affects brain function

Enteroviral encephalomyelitis involves both brain and spinal cord

Enteroviral poliomyelitis-like syndrome mainly affects motor neurons in the spinal cord, causing weakness that can range from flaccid weakness (paresis) to flaccid paralysis typically with reduced muscle tone and diminished reflexes.

Enteroviral poliomyelitis-like syndrome (in relation to enteroviral encephalomyelitis)

Enteroviral poliomyelitis-like syndrome is a neurological condition caused by enteroviruses affecting the motor neurons (anterior horn cells) in the spinal cord.

These neurons control voluntary muscle movement.

It may occur:

On its own, with mainly spinal motor neuron involvement, or as part of enteroviral encephalomyelitis, where there is broader inflammation of the brain and spinal cord

This means it sits within a spectrum of enteroviral central nervous system infections, rather than being a completely separate condition.

What happens in the body?

When motor neurons are affected:

Muscles lose their nerve supply (denervation)

This leads to a lower motor neuron pattern of weakness

Weakness can range from:

Flaccid weakness (paresis)

to flaccid paralysis,

Typically with:

Reduced muscle tone

Diminished or absent reflexes

Symptoms

Symptoms often develop suddenly, sometimes after a mild viral illness.

They may include:

Weakness in one or more limbs (often asymmetric)

Difficulty moving an arm or leg

Reduced muscle tone (floppiness)

Reduced or absent reflexes

If there is overlap with enteroviral encephalomyelitis, additional symptoms may occur, such as:

Confusion or Altered Consciousness

Seizures

Speech (Dysphonia, Dysarthria or Aphasia) or Swallowing Difficulties (Dysphagia)

Coordination problems (Ataxia or Dysequilibrium)

Muscle wasting (atrophy)

If motor neuron damage persists:

Muscles may gradually waste (atrophy) over days to weeks

Affected limbs may become thinner

Weakness may not fully recover

Muscle wasting is:

More likely in severe or prolonged cases

A sign of lower motor neuron injury

Usually localised to affected muscles

Paraplegia

In more severe cases, both legs may be affected, leading to paraplegia (paralysis of the lower limbs).

This is:

Uncommon

Usually associated with extensive spinal cord involvement

More likely when there is overlap with enteroviral encephalomyelitis

Paraplegia is typically:

Flaccid (reduced tone)

Associated with reduced or absent reflexes

Recovery

Recovery varies:

Some people recover fully

Others have partial recovery with ongoing weakness

Some may have long-term weakness or paralysis

Recovery can take weeks to months, and rehabilitation is often needed.

Key point

Enteroviral Poliomyelitis-like syndrome:

Affects spinal motor neurons

Causes muscle weakness ranging from motor weakness (paresis) to flaccid paralysis

May occur alone or as part of enteroviral encephalomyelitis

Can lead to muscle wasting and, rarely, paraplegia

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Aseptic meningitis is one of the most common neurological manifestations of enterovirus infection. It refers to inflammation of the meninges (the protective membranes surrounding the brain and spinal cord) in the absence of bacterial infection.