3Naming the Malformations: Jackler, Sennaroğlu and Grover

FJackler 1987 — the first embryogenesis-based map

Carlo Mondini gave the first description of a malformed inner ear in 1791 — a cochlea of one and a half turns with a normal basal turn — but the first systematic, embryology-anchored classification came from Jackler, Luxford and House in 1987. Jackler's insight was to organise malformations by the timing of developmental arrest, producing an ordered series: complete aplasia (Michel), common cavity, cochlear aplasia, cochlear hypoplasia and incomplete partition. This arrest-timing logic — earlier arrest, more missing — is the conceptual backbone that every later scheme inherited. Its limitation, recognised even then, is that imaging of the era could not resolve the fine internal anatomy that later distinguished the partition subtypes.[1987]

TSennaroğlu 2002 and the 2017 update — the working standard

Sennaroğlu and Saatci's 2002 scheme became the most widely used classification worldwide, mapping each malformation to candidacy, electrode choice and gusher risk rather than describing it in isolation. Its central contribution was to split incomplete partition into distinct types: IP-I (a cystic cochlea with no modiolus and a high gusher risk), IP-II (the classic Mondini deformity — a deficient apical modiolus, the mildest and most often paired with an enlarged vestibular aqueduct), and IP-III (an X-linked deformity with a deficient modiolar base, the highest-gusher form). The 2017 update with Bajin refined these categories and added the rudimentary otocyst and, crucially, criteria for the cochlear aperture and the bony cochlear nerve canal — the first formal nod toward the nerve. By tying anatomy to action — which electrode, which gusher precaution, whether to consider an auditory brainstem implant — Sennaroğlu's system is the one most surgical teams actually speak.[2002][2017]

TGrover 2019 — the SMS morphological scheme

Grover and colleagues proposed the SMS classification in 2019, grading the malformation on three measurable morphological features: the size and shape of the cochlea, the state of the modiolus, and the integrity of the lamina cribrosa. Rather than reasoning from embryology, SMS reads what the scan actually shows and converts it into a surgical-difficulty estimate, an approach intended to be reproducible across observers. It explicitly aims to predict the operative challenges — the gusher, the electrode that will seat — that a clinician faces in the room. SMS is best seen not as a replacement for Sennaroğlu but as a complementary, morphology-first lens on the same ears.[2019]

CThe shared blind spot: the nerve

All three classical systems describe the bony and membranous cochlea in increasing detail, yet none of them, in its original form, grades the cochlear nerve — the very structure that determines whether an implant can ever work. They also overlap at the edges: intermediate and transitional forms blur the line between cochlear hypoplasia and common cavity, so the same ear can be labelled differently by different observers. Because candidacy hinges on the nerve and because real ears resist tidy boxes, a purely morphological label is necessary but not sufficient for planning. This gap — anatomy named beautifully but the nerve and the outcome left unsaid — is exactly what motivates the prognosis-oriented, hearing-and-nerve-driven algorithm developed later in this chapter.[2017][2019][1987]