Diagnosis
is based on a thorough personal and family medical history, physical examination
(including a neurological exam), and a series of laboratory tests. The
physician will ask about recent changes in intellectual or emotional function,
which may be early signs of Huntington's disease.
Before
the advent of a genetic blood test, the diagnosis of HD(Huntington’s disease)
was based upon the typical clinical presentation and a positive family history
of HD, supported by the findings of atrophy (shrinkage) of the caudate nucleus
on brain imaging. Today, DNA testing can reliably diagnose HD and differentiate
the disease from other disorders that cause similar symptoms. DNA testing is
also available for family members of patients with HD who may not have symptoms
but are at risk for the disease. However, because of potential psychological
and legal implications of identifying a HD gene mutation in an asymptomatic,
at-risk individual, predictive testing should be performed by a team of
clinicians and geneticists who are knowledgeable about the disease and genetic
techniques and who are sensitive to the psychosocial and ethical issues
associated with such testing.
♣ Genetic Testing
Genetic
testing involves taking a blood sample for DNA analysis to determine whether
the distinct mutation for Huntington's disease has occurred in gene IT-15. A
sample of DNA also may be required from a closely related affected relative,
ideally a parent. This helps confirm the diagnosis of HD and is important if
the family's history is in any way unclear, uncertain, or unusual. Persons who
test positive and are considering pregnancy are advised to seek genetic
counseling before they conceive.
Presymptomatic
testing can be performed on adults, children, and even fetuses in the womb.
Genetic testing of a fetus holds special challenges and risks, and some testing
facilities choose not to do it.
At-risk
couples wanting to have children may choose to undergo in vitro fertilization
with preimplantation screening. In this procedure, embryos produced from the
couple's sperm and eggs are screened to identify one that is free of the HD
mutation, which is then implanted in the woman's uterus.
A positive
test result can have profound, unanticipated impacts on patients and their
families. Anyone contemplating genetic testing should obtain testing guidelines
from the testing center or from an organization devoted to the interests of
Huntington's disease patients and their families. Guidelines recommend that
testing centers follow these practices:
Counseling
should be provided before and after the test, and before the results are known.
☞ Test results should be strictly confidential and
should be disclosed only in person, and only to the individual being tested,
regardless of the outcome.
☞ To protect the interests of minors, including
confidentiality, testing should not be conducted for persons under 18 without a
compelling medical reason, such as the appearance of HD symptoms in a child.
♣ Computed
Tomography (CT scan)
This
painless diagnostic procedure produces computer-generated images of the brain's
internal structures. Patients with HD often show shrinkage in two areas of the
brain - the caudate nuclei and putamen - and enlargement of cavities within the
brain called ventricles. The presence of these structural changes is not
conclusive for Huntington's disease nor does their absence rule it out.
CT scans combined with other procedures such as magnetic resonance imaging (MRI scan) and/or positron emission tomography (PET scan) can be a helpful diagnostic tool, especially when evaluated in the context of family history and clinical symptoms.
%E2%80%99s+Diagnosis1.jpg)
