Condition · Central / brainstem

Intra-axial Brainstem Lesion

Crossed pathway interrupted — diagonal reflex pattern

Crossed versus uncrossed pathways

The contralateral (crossed) reflex requires the signal to cross the midline of the brainstem; the ipsilateral (uncrossed) reflex does not. A midline intra-axial lesion can selectively interrupt the crossed pathways, sparing the uncrossed ones.

Reading the diagonal

On the 2x2 grid, the contralateral cells form one diagonal and the ipsilateral cells the other. Abnormal contralateral cells with normal ipsilateral cells is the brainstem signature.

The reflex signature

Stim. Right
Stim. Left
Probe Right
Present
90 dB HL
Absent
Probe Left
Absent
Present
95 dB HL
The characteristic four-cell grid for this condition.

Both contralateral cells are absent while both ipsilateral cells are normal — a diagonal pattern.

Reflex decay

0s2s4s6s8s10s0%50%100%50% criterion
Negative (normal) decay — amplitude is well maintained across the 10-second hold. Decay may be present and is variable; the crossed/uncrossed dissociation is the more reliable sign.

Pure-tone audiogram

0204060801002505001k2k4k8kFrequency (Hz)Hearing level (dB HL)
○ Right ear✕ Left ear
Hearing is often normal or near-normal — the lesion is central to the cochlea.

Frequencies plotted: 250, 500, 1k, 2k, 4k, 8k Hz.

References for this page

  1. Jerger S, Jerger J (1977). Diagnostic value of crossed versus uncrossed acoustic reflexes: Eighth nerve and brainstem disorders. Archives of Otolaryngology, 103(8), 445–453.
  2. Jerger J, Jerger S, Hall JW (1979). A new acoustic reflex pattern. Archives of Otolaryngology, 105(1), 24–28.
  3. Musiek FE, Baran JA (2007). The Auditory System: Anatomy, Physiology and Clinical Correlates. Pearson, Allyn & Bacon, Boston.
  4. Katz J (Ed.) (2015). Handbook of Clinical Audiology (7th ed.). Wolters Kluwer, Philadelphia.
Want to contrast this with another condition? The comparison tool places any two reflex signatures side by side.