1Our Philosophy: The Rational Checklist

FWhy a checklist, and why this one

Cochlear implantation has become the mainstay of management for severe-to-profound sensorineural hearing loss, and imaging is now a routine part of the work-up — used to confirm that there is an implantable cochlea and a cochlear nerve, to anticipate surgical difficulty, and to help predict outcome. Yet the literature offers no firm consensus on the modality of choice, and many centres simply obtain both a high-resolution CT and an MRI on every candidate. That default carries real costs: scanner time and money, ionising radiation, and — in young children — a separate general anaesthetic for the CT. The protocol described here was developed and tested prospectively, with institutional ethics approval, to replace the default with a deliberate, candidate-specific strategy.[2026][2012]

FMRI-predominant, selective HRCT

The core rule is simple: MRI screens everyone; HRCT is added only when it will change the plan.Every candidate — pre-lingual or post-lingual — has MRI of the brain and temporal bone, which shows the cochlear fluid signal, the cochlear nerve in the internal auditory canal, the brain and the cerebellopontine angle without radiation. HRCT is reserved for defined risk features — a history of meningitis, chronic ear disease or previous surgery, conductive or asymmetric loss, syndromic and cranio-facial anomalies, atresia or trauma — and for any inner-ear malformation seen on the MRI. The approach agrees with Mackeith and with Siu’s selective imaging paradigm before paediatric implantation.[2026][2019]

CThe MRI fishbone — six steps, brain inward

The screening MRI is read as a fixed six-step sequence worked from the brain inward, so nothing is missed: the brain (white-matter lesions, TORCH sequelae, tumours), the cerebellopontine angle (lesions, vestibular schwannoma), the internal auditory canal (hypoplasia, aplasia, schwannoma), the cochlear aperture (narrowing or absence), the vestibulo-cochlear apparatus (cochleovestibular malformations) and the middle ear and mastoid. The proximal steps catch what excludes or redirects a candidate; the distal steps anticipate the operation.[2026]

CThe HRCT inside-out — lumen outward

When HRCT is indicated, it is read from the cochlea outward, in order of what matters most to the decision: first the cochlear lumen (is there a patent scala to implant, or ossification and malformation?), then the cochlear nerve canal and aperture and the internal-auditory-canal calibre (a bony proxy for whether there is a nerve to stimulate), then the facial nerve and the vascular and access anomalies that make surgery harder. The two innermost rings settle candidacy; the outer ring briefs the surgeon.[2026]

CWhat the rational checklist buys

Used together, the protocol and its two checklists do three things. They save cost, radiation and anaesthesia by sparing the candidates who need only an MRI. They exclude the unsuitable early — a complete cochlear aplasia or an aplastic cochlear nerve is found on the screening MRI, redirecting toward an auditory brainstem implant before any further work-up. And they impose a reproducible discipline on the read, so that candidacy, surgical risk and electrode choice all fall out of the same structured look. The rest of this chapter works through each structure in the checklists in turn.[2026][2019]