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| This news site is not sanctioned by, nor part of, the Diamond Headache Foundation, The American Academy of Neurology OR The American Headache Society. |
| News covering selected sessions related to migraine from 2008 medical conferences. |
| Annual Meeting of the American Academy of Neurology |
Chicago, IL April 15-18, 2008 |
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Lachance First Clinical Data Released on
Outbreak of Immune Polyradiculoneuropathy in Pork
Processors |
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BY MARY JO DALES
Editorial Director |
CHICAGO —
Clinical data and lab findings from a new disease called immune
polyradiculoneuropathy were unveiled at the annual meeting of
the American Academy of Neurology.
Immune polyradiculoneuropathy has been observed in workers
exposed to pig brains in pork processing plants. The disorder is
thought to be triggered by an immune-mediated response that
occurs when aerosolized brain tissue from pigs is inhaled, but
the exact mechanism is not yet understood.
The disease has now been diagnosed among 18 workers at an
Austin, Minn., pork-processing plant where all were exposed to
pig brains. Only two other pork-processing plants in the United
States, one in Indiana and another in Nebraska, also are thought
to perform brain extractions. A similar pattern of illness has
been seen in at least five workers at the Indiana plant and one
worker at the Nebraska plant. All three plants have halted the
brain extraction process, Dr. Jim Sejvar, a neurologist and
epidemiologist from the Centers for Disease Control and
Prevention in Atlanta, said during a press conference at the
meeting.
The news of these cases has been reported in the popular press
and initial epidemiologic details were reported in the CDC’s
Morbidity and Mortality Weekly
Report on Feb. 8.
At the meeting, Dr. Daniel Lachance of the Mayo Clinic in
Rochester, Minn., described what he called the first extensive
clinical data on these cases, including “a never before seen”
pattern of neural autoantibodies. The IgG staining pattern was
found consistently in all 18 Minnesota workers evaluated at the
clinic.
Dr. Lachance has not reviewed cases from workers at the other
two plants.
The closest clinical parallels to this new disorder are
paraneoplastic neurologic disorders, which are triggered by
autoimmune responses in patients with cancers,
he said. The new disease holds the possibility of providing a
unique glimpse into
how autoimmune reactions might trigger neurologic disorders.
The 18 affected workers in the Mayo study ranged in age from 20
to 50 years
old. Most were Hispanic, as is most of the plant workforce.
Nearly all presented with
weakness, mainly in the upper and lower extremities, and
fatigue. They had pain in
their extremities and decreased sensation or tingling.
The clinical pattern is one of subacute, sensory-predominant
polyradiculoneuropathy, he said.
Dr. Lachance similarly shared MRI images from the patients,
showing enhanced and thickened spinal roots, as well as the
results of electrophysiologic testing, indicating a mixture of
demyelinating and axonal features with prolonged motor and
F-wave latencies. Quantitative sensory testing indicated a mix
of large and small fiber abnormalities. Nearly all of the
patients had elevated levels of CSF protein, with values ranging
from 23 to 231 mg/dL.
The treatments for these patients have been largely pain relief
using drugs typically prescribed for neuropathy patients,
intravenous methylprednisone, and intravenous immunoglobulin.
Dr. Lachance said that the first hints of the novel disease
emerged from two patients who were working at the Minnesota
plant. Both were suspected to have acute transverse myelitis,
were treated with steroids, and improved after a few months. But
as soon as they were well enough to return to work, their
symptoms returned within about a month after resuming their
jobs.
As a result of the findings, the workplace nursing staff for the
processing plant, with the aid of a Spanish-speaking interpreter
from Mayo Health System, interviewed other workers at the plant
in September 2007. By November, 12 suspected cases of the
neurologic disorder were uncovered and reported to the Minnesota
Department of Health. Within less than 1 month, epidemiologists
had determined that all of the cases were among people who
worked near or were directly involved in the harvesting of pig
brains. In the procedure, compressed air is forced into the
pig’s foramen magnum, creating
a fine mist that contains emulsified brain tissue that can be
inhaled. Exposure to the porcine brain tissue is purported to be
the trigger for the disorder.
In December, the Minnesota plant halted the harvesting of pig
brains. Subsequently, a survey found that the two other
processing plants performed a similar
brain extraction process. Both stopped the brain extractions.
During a press conference held at the meeting, Dr. Sejvar
strongly discounted
the possibility that the disease is the result of an infectious
process. Evaluations indicated that none of the pigs were sick,
that there is no evidence for a foodborne illness, and that the
disease clearly has not been transmitted from person to person. |
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