Large vestibular aqueduct: large endolymphatic sac?

The first description of large vestibular aqueduct (LVA) was by Carlo Mondini in 1791 from his dissection of the temporal bones of a boy born deaf (Mondini, 1791) Mondini not only described and drew the LVA which he measured at seven lines or about 15 mm wide, but he opened the voluminous endo-lymphatic sac which he found to be 'full of a rather viscous humour, clear and yellowish which obviously flowed from the vestibule'. Mondini also noted that 'the bony plate was missing which protects the aqueduct of the vestibule like a scale whose uneven edge forms that chink which is clearly visible in the posterior face of the pyramid'. Mondini's precise and detailed account was of a congenital malformation of the inner ear consisting of a grossly enlarged vestibular aqueduct and endolymphatic sac and duct, a larger than normal vestibule, a normal basal turn of the cochlea, but with the distal 1.5 coils replaced by a sac; ('amplam caveam cavitati ultimi gyri responden-tem;). Thus there can be no doubt as to what Mondini actually described but unfortunately the term 'Mon-dini's dysplasia' has been so grossly abused subsequently as to make it virtually meaningless. The first description of LVA based on imaging was by Valvassori and Clemis in 1978 who showed LVA in 50 patients by polytomography and coined the description 'large vestibular aqueduct syndrome' when this was accompanied by sensorineural hearing loss. Subsequently, the ease with which an LVA can be demonstrated by axial computed tomography (CT) has meant that a plethora of accounts of LVA based on CT has been published, such as those of Emmett (1985) and Levenson et al. (1989). However in an account of another large series of LVA, Jackler and De La Cruz drew attention to the poor results of shunt operations to attempt 'stabilisation' of hearing (Jackler and De La Cruz, 1989). In a previous editorial on LVA, I indicated the probable association with enlargement of the endo-lyphatic duct and sac (Phelps, 1994) and this has been borne out by histological studies firstly by Kodama and Sando in 1982 and Gussen in 1986. These Mondini-type deformities of cochlear and vestibular systems were perhaps surprisingly considered by these authors to be the result of pressure erosion of bone, although there was no evidence of Meniere-type endolymphatic hydrops in the dissections. Meantime, significant advances in magnetic resonance imaging (MRI) have meant that it is now …