Neurophysiological Testing 2019-03-09T15:54:27+00:00

Neurophysiological Testing

  • Electromyogram (EMG) shows chronic partial denervation.
  • Nerve conduction studies (NCS) show a sensory>motor axonal neuronopathy in RTD Type 2 but may not show sensory involvement in RTD Type 3.
  • Motor nerve conduction velocities are usually normal.
  • Sensory nerve action potentials (SNAP) are often absent in RTD Type 2 with variable findings in RTD Type 3.
  • Visual evoked potentials (VEP) are frequently abnormal in RTD Type 2 with variable findings in RTD Type 3.


Audiologic Test Findings

The diagnosis of ANSD in RTD is based on a characteristic pattern of results on hearing assessments performed by audiologists.  In RTD the most common audiological test findings included:

  • Absent or abnormal auditory brainstem response (ABR / BAEP) with cochlear microphonic present.
  • Otoacoustic emissions (OAE) are often present but found to disappear over time in many patients.
  • Acoustic reflexes often absent.
  • Magnetic resonance imaging (MRI) is generally normal without any evidence of VIII cranial nerve hypoplasia.