Syndrome of Acute Flaccid Myelitis in Children
Dr. Peter Bernad, M.D., MPH, FACP
Recently there have been reports of a “new” condition as reported in various journals and recent publications regarding an outbreak nationwide of acute flaccid myelitis in children.
In the past, this syndrome was invariably caused by an infection of 1 of the 3 types of polio virus. The mere mention of polio virus raises concerns among the American population, as well as physicians who are used to practicing in the 1950s into the 1960s. There are illnesses that clinically resemble polio virus infection that is polio, which may be caused by other Enteroviruses. These include Coxsackie viruses groups A and B, Japanese Encephalitis Virus, West Nile Virus, and now the cases of acute flaccid myelitis seen in children. There have been a number of deaths reported nationwide. This particular illness is thought to be related to an Enterovirus 68. That link is still being confirmed.
There have been epidemics of hemorrhagic conjunctivitis, which is thought to be caused to Enterovirus 70. These had been seen in Asia and Africa, less so in the United States. They have been associated with lower motor neuron paralysis resembling poliomyelitis. Fortunately, poliomyelitis has been almost eradicated because of excellent vaccination programs and because of public health.
The paralytic disease that is most reminiscent of the new acute flaccid myelitis in children is the old scourge of polio.
Vaccination has been practiced in the United States for many years and, therefore, the crippling effects that are reminiscent of poliomyelitis are no longer seen. As a neurologist over the last 30 years, I have never seen a single new patient with poliomyelitis. My forefathers in medicine, colleagues in the 1950s, saw many cases. In the summer of 1955, the last polio epidemic was witnessed. There were 3950 cases of acute poliomyelitis in Massachusetts alone with 2771 of these cases being paralytic. The details of this epidemic were described by Pope and Colleagues. This has been covered in the Principles of Neurology of Adams and Victor’s classic textbook of neurology. Only a few cases are reported around the world of paralytic poliomyelitis. These are divided between unvaccinated children and unvaccinated adults, the latter exposed to recently vaccinated infants. Unfortunately, there are still some patients who have the residual of the old polio from previous epidemics. One of the conditions is called the postpolio syndrome. These are seen with patients who have delayed progression of muscle weakness, which appear many years after the acute paralytic illness. There are patients who have recovered from paralytic poliomyelitis and developed progressive muscular weakness, sometimes 40 years after, and in some ways this is related to the previous infection in childhood. The exact cause of this late developing weakness is somewhat obscure.
Poliomyelitis is a highly communicable disease. The main reservoir of infection is the human intestinal tract. The main route of infection is fecal-oral hand-to-mouth as it relates to an enteric pathogen. The virus multiples in the pharynx and intestinal tract. The incubation period is 1-3 weeks. In only a small fraction of patients is the infection seen in the nervous system. Most patients are asymptomatic. The interest currently is in the acute flaccid myelitis seen in children, which have been reported in multiple states. Please see http://bit.ly/myelitis/nt. This condition is a focal limb weakness. Abnormalities in spinal cord gray matter on magnetic resonance imaging have been seen, and it is linked to an outbreak of upper respiratory infection caused by Enterovirus 68, which is still being evaluated. There have been verified cases of more than 70 patients in 29 states, and there are several other additional reports. Many pediatric neurologists have seen cases all across the United States. Treatment guidelines have been developed for acute flaccid myelitis. I would estimate that there are well over 100 patients by this time, and the following criteria are noted: 1) The patient is no older than 21 years of age and shows an acute onset of focal limb weakness with an MRI showing a spinal cord lesions largely restricted to gray matter. These new cases must have also occurred on or after 08/01/2014. For our readers who are interested, there are more updates on the surveillance of cases of acute flaccid myelitis in the CDC website at http://bit.ly/cdc/myelitis. At this point, only symptomatic treatment is known. Careful observation of swallowing function, breathing, vital capacity, pulse, and blood pressure in anticipation of respiratory and circulatory complications are necessary. Paralysis of the limbs with physical therapy, occupational therapy, foot boards, hand and arm splints, knee and trochanter rolls are helpful to prevent foot drop and other deformities. Passive movements may help prevent contractures and ankylosis. Respiratory failure due to paralysis of the intercostal and diaphragmatic muscles or to depression of the respiratory centers in the brain stem calls for the use sometimes of respirators. Tracheostomy may have to be also performed. The management of pulmonary and circulatory complications is reminiscent of the management of diseases such as myasthenia gravis and Guillain-Barre syndrome and best carried out in special hospitals with urologic intensive care units and respiratory units. After stabilizing the patient and confirming and documenting stability, the patient may be transferred to an LTAC, which is a long-term acute care facility. The LTACs are specialized hospitals and facilities that cater to patients on respirators and are staffed with excellent and expert physicians. I am not aware of any specific antiviral therapy or potency of such therapies.