Post-labyrinthectomy & central compensation

Two SHA reports from the same patient, months apart. The labyrinth is permanently gone — and yet, by the second visit, the chair report has almost normalised. This is the single most important demonstration of what RCT does that no other vestibular test can.

Acute pattern

In the days following a surgical labyrinthectomy (or vestibular neurectomy for intractable Ménière's disease), the patient shows the deepest acute peripheral pattern: gain markedly reduced across all frequencies, phase lead elevated by 20° or more, directional preponderance toward the intact side > 30 %, and step-test Tc collapsing toward the cupula value.

Compensated pattern (≥ 6 months)

By six months gain across the SHA band has recovered into the normal range. Phase lead has fallen toward the upper end of normal. Symmetry is back inside the ±22 % band. Yet the caloric test on the operated side remains a flat trace.

Monitoring with RCT

Routine follow-up SHA at 1, 3 and 6 months gives a quantitative recovery trajectory. Failure of expected recovery — for example, persistent asymmetry > 22 % at 6 months — should prompt review of the rehabilitation programme and a search for additional pathology.

Other unilateral lesions

• Vestibular neurectomy — same physiology, same RCT trajectory.
• Gentamicin chemoablation for Ménière's — partial deafferentation; expect intermediate findings.
• Post-vestibular schwannoma resection — slow tumour growth pre-compensates; the post-operative deficit is therefore often less dramatic than after labyrinthectomy.