Critical Care Medicine

Neuromuscular Weakness in Children: Transverse Myelitis

Transverse myelitis

1. Description of the problem

Acute transverse myelitis (ATM) historically connotes a non-infectious, inflammatory process involving, predominantly, sensory and motor myelinated pathways within the spinal cord. In contrast with poliomyelitis, the disorder tends toward symmetrical involvement of the spinal cord.

Pain is often a herald symptom, often maximal around the level of inflammation in the spinal cord. However, the symptom can be diffuse, with radicular components involving the extremities. Tonic spasms may be prominent early in the course of the disease. Severe muscle pain and intense tenderness to palpation are not typical features in ATM.

Transverse myelitis may occur in isolation or as part of a more of a widespread process, acute demyelinating encephalomyelitis (ADEM). It may also be the initial manifestation of chronic diseases, such as multiple sclerosis or neuromyelitis optica.

2. Emergency Management

Once a provisional diagnosis has been established and the patient's vital signs are secured, treatment should be initiated with high dose intravenous corticosteroids:

- Methylprednisolone. 30/mg/kg/day divided BID or TID

High-dose corticosteroids should be continued for 3-5 days depending on the patient's clinical response. Some authors have advocated addition of IVIg or plasmapheresis in refractory cases. There is, however, no systematically collected evidence that supplemental treatment is efficacious after the initial progressive phase of the disease.

After the initial high-dose parenteral regimen, corticosteroids should be continued orally and gradually tapered over an extended phase of from 6-8 weeks to avoid a treatment rebound relapse of symptoms.

3. Diagnosis

Pain is frequently a herald symptom, often maximal around the level of inflammation in the spinal cord. However, the symptom can be diffuse, with radicular components involving the extremities. Tonic spasms may be prominent early in the course of the disease. Severe muscle pain and intense tenderness to palpation are not typical features in ATM.

The most important clinical diagnostic characteristic is the presence of a "sensory level" corresponding to a somatotopical pattern of sensory loss that may not be congruent with the level of motor involvement. There may also be disassociated sensory loss with relative sparring of spino-thalamic modalities located in the ventral spinal cord in comparison to posterior column functions running in tracts located on the opposite side of the cord.

The pattern of sensory and motor functional disturbance reflects the distribution of the lesion within spinal cord parenchyma. The presence of a discrete sensory level probably excludes poliomyelitis from the differential diagnosis, but not other direct infections of the spinal cord, or intrinsic or extrinsic mass lesions. Hence, emergent imaging of the cord is required to alleviate concerns about spinal cord compression.

Established diagnostic criteria for transverse myelitis require confirmation of an inflammatory process by virtue of evidence of inflammatory changes in the CSF formula or the presence of contrast enhancement on MRI examination.

The diagnosis of transverse myelitis is based on typical features on clinical examination, spinal fluid examinations and MRI studies of the brain and spinal cord. In addition to routine studies, CSF analyses should include:

  • Investigation for commonly associated viral and bacterial pathogens.

  • The presence of oligiclonal bands.

  • CSF IgG Index.

  • Anti-aquiporin-4 antibodies.

The most common MRI abnormalities are:

  • Increased signal on T2 and FLAIR spin-echo sequences.

  • Focal swelling of the spinal cord.

Contrast enhancement of cord parenchyma or contiguous spinal roots may also be evident. A careful survey of structures rostral to the foramen magnum is essential to ascertain whether the ATM is part of ADEM or may be the first clinical manifestation of incipient multiple sclerosis (MA) or neuromyelitis optica (NMO). In otherwise typical ATM, initial imaging studies are normal in roughly 20% of patients. Followup studies, however, are often informative.

After the onset of symptoms, the course of the disease unfolds over hours to days. A hyperacute evolution of symptoms in under 4-6 hours should suggest an alternative diagnosis, such as spinal cord hemorrhage or infarction.

Pathophysiology

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Epidemiology

The incidence of transverse myelitis in children varies both geographically and over time, however, not in a predictable fashion. Incidence rates approximate 1-4 per million individuals under the age of 18, or roughly 1/10th the incidence of GBS.

The disease is associated with a number of infections that may precede the ATM or evolve concurrently. Sorting out direct infection as opposed to a post-infectious autoimmune event may be difficult. ATM has been best described as a post-infectious entity in association with viral infections, especially within the herpes lineage, including Epstein-Barr virus, herpes simplex virus, cytomegalovirus, and hepatitis viruses. It is also well described with mycoplasma.

Approximately 60% of individuals are able to identify potentially triggering events which occurred over the 6 weeks prior to the onset of neurological symptoms. The most common are:

  • Upper respiratory tract infections.

  • Gastroenteritis.

A host of other events follow including vaccines, skin infections, trauma, parturition, animal bites and insect bites. Immunizations are frequently incriminated in sorting out pathogenesis; however, large-scale epidemiological studies have failed to indicate a causal relationship with any of the current vaccines incorporated in recently recommended routine immunization regimens.

Prognosis

Although somewhat inconsistent, the literature suggests a good prognosis for recovery. Approximately 50% of children will have a complete recovery, with another 25-30% having residual symptoms but achieving independent ambulation. There are no definite markers for a good outcome but those characteristics which augur poorly are:

  • Onset at an early age (less than 2 years).

  • Flaccid paraplegia at the time of presentation.

  • High cervical involvement.

The risk of subsequently developing multiple sclerosis is considerably less in children compared to adults. Roughly 5% of children will have recurrences of ATM or go on to develop chronic demyelinating disease.

Special considerations for nursing and allied health professionals.

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What's the evidence?

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