Porphyria Educational Services
PORPHYRIA EDUCATIONAL SERVICES BULLETIN Vol. 1 No.2 January
1999
DIAGNOSIS OF PERIPHERAL NEUROPATHY
The diagnosis of peripheral neuropathies can be frustrating, and
even
painful. Diagnosis also is very time consuming not to mention
that it is
very expensive.
To obtain a correct PN diagnosis, a porphyric must first have
careful
clinical and electrodiagnostic assessment. This assessment must
be carried out with
attention to the pattern of involvement and the types of nerve
fibers most
affected.
The reason for this is that it both narrows the differential
diagnosis and
helps to focus the laboratory evaluation. An algorithmic approach
to the evaluation and
differential diagnosis of a patient with peripheral neuropathy is
presented.based on several important elements.
These elements include use of the clinical history and physical
examination, the use of electromyography and nerve conduction
studies,
and autonomic testing.
In addition there are cerebrospinal fluid analysis and nerve
biopsy
findings.
The underlying cause of axonal neuropathies can frequently be
treated;
demyelinating neuropathies are generally managed with the
assistance of a
neurologist, however a neurologist can be a consulting physician
to one's
primary physician after a PN diagnosis has been established by
the neuro.
The incidence of peripheral neuropathy is not known, but it is a
common
feature of many systemic diseases. Diabetes and alcoholism are
the most
common etiologies of peripheral neuropathy in adults living in
developed
countries.
The primary worldwide cause of treatable neuropathy is
leprosy.
Neuropathies associated with human immunodeficiency virus (HIV)
infection
account for an increasing number of cases.
Peripheral neuropathy has numerous other causes, including
hereditary,
toxic, metabolic, infectious, inflammatory, ischemic and
paraneoplastic
disorders. The number of peripheral neuropathies for which an
etiology
cannot be found despite extensive evaluation ranges from 13 to 22
percent.
Many undiagnosed patients (up to 42 percent) are found, after a
careful
family history and examination of kin, to have a familial
neuropathy. This is
where the acute hepatic porphyrias come in.
The evaluation of a peripheral neuropathy can be time-consuming
and costly
but is less so if established after documented porphyria has been
diagnosed.
.
A systematic approach based on a careful clinical and
electrodiagnostic
assessment can help narrow the possibilities and tailor the
laboratory
evaluation to a specific differential diagnosis.
Diabetes and alcoholism are the most common causes of peripheral
neuropathy in the United States, but since 1991 a large number of
PN cases have been
documented stemming from one of the acute hepatic porphyrias.
The most common presentation of peripheral neuropathy is distal
symmetric
sensorimotor dysfunction.
It most often begins to appear at the onset of an acute attack
and based
on the occurrence of such attacks and their severity, PN may las
from a few days
to a few weeks. It can sometimes end in respiratory paralysis and
death.
Resources:
Adams, R.A., MD, Peripheral Neuropathy, 1994, Journal of
Neuromedicine.
No. 8. pp. 34-39.
ANN NOELLE PONCELET, M.D.,University of California, San
Francisco, San
Francisco, 1997.