Brainstem auditory evoked responses in leukodystrophies

Area of Science:

• Neurology
• Neurophysiology
• Genetics

Background:

• Leukodystrophies are a group of inherited genetic disorders that affect the myelin sheath in the nervous system.
• Brainstem auditory evoked responses (BAERs) assess the integrity of the auditory pathway from the cochlea to the brainstem.

Purpose of the Study:

• To evaluate the utility of BAERs in diagnosing and characterizing Pelizaeus-Merzbacher disease (PMD), adrenoleukodystrophy (ALD), and metachromatic leukodystrophy (MLD).
• To determine if BAERs can differentiate leukodystrophies from progressive gray matter diseases.

Main Methods:

• BAERs were recorded in patients diagnosed with PMD, ALD, and MLD.
• BAERs were also recorded in known carriers of PMD.
• Electroencephalography (EEG) data was analyzed in conjunction with BAERs.

Main Results:

• All 10 patients with leukodystrophy exhibited altered BAERs, with 9 showing severe abnormalities.
• A single patient with ALD, asymptomatic at the time, displayed minimal BAER abnormality (prolonged wave V latency).
• In 9 patients, only wave I (and sometimes wave II) was recorded, with subsequent waves absent. No BAER abnormalities were found in PMD carriers.

Conclusions:

• BAERs are a sensitive indicator of auditory pathway dysfunction in leukodystrophies.
• The specific pattern of BAER abnormalities can help in assessing disease severity.
• Combining BAERs with EEG aids in distinguishing leukodystrophies from other neurological disorders affecting gray matter.