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We investigated whether vestibular dysfunction may cause or contribute to postural imbalance and falls in patients with Niemann-Pick type C disease (NP-C). Eight patients with NP-C disease and 20 healthy controls were examined using the video-based head impulse test (vHIT) and caloric irrigation to investigate horizontal canal function as well as ocular- and cervical vestibular evoked myogenic potentials (o- and cVEMP), and binocular subjective visual vertical estimation (SVV) for otolith function, and static posturography. There were no significant differences in vestibulo-ocular gain, caloric excitability, o-/cVEMP measures or SVV between the two groups. Posturographic total sway path (tSP) and root mean square (RMS) were significantly higher in NP-C than in controls in 3 out of 4 conditions. The Romberg quotient (RQ) to assess the amount of visual stabilization was significantly lower in the NP-C than in the HC group. In contrast to other inherited metabolic disorders, such as Morbus Gaucher type 3, we did not find any evidence for an impairment of canal or otolith function in patients with NP-C as their cause of postural imbalance. Since RQ was low in NP-C patients, indicating proper sensory input, the observed increased postural sway is most likely due to a cerebellar dysfunction in NP-C, which may therefore, explain postural imbalance.

Background: The aim of this work is to compare the microstructure of cornea verticillata in Fabry disease with amiodarone-induced keratopathy by means of in vivo confocal laser-scanning microscopy (CLSM)., Methods: Ten eyes of ten patients suffering from Fabry disease, six eyes of six patients with amiodarone-induced keratopathy and eight eyes of healthy control subjects were examined by conventional slit-lamp microscopy and CLSM. One Fabry patient received amiodarone therapy. All Fabry patients were under enzyme replacement therapy with agalsidase alfa., Results: Seven out of ten Fabry patients and all patients receiving amiodarone showed typical cornea verticillata on slit-lamp examination. CLSM revealed hyper-reflective intracellular inclusions in basal epithelial cells of all Fabry patients with cornea verticillata and in one Fabry patient without slit-lamp-detectable vortex keratopathy, as well as in all eyes featuring amiodarone keratopathy. Amiodarone deposits were more reflective and of grossly different size. Seven Fabry patients and all amiodarone patients had stromal microdots. Two amiodarone patients showed amiodarone inclusions in the endothelium. The number of CLSM changes in Fabry patients did not correlate with that of slit-lamp detectable cornea verticillata., Conclusions: While Fabry-induced cornea verticillata and amiodarone keratopathy cannot be distinguished by conventional slit-lamp microscopy, CLSM allows the differentiation between both etiologies in the majority of patients. CLSM appears to reveal corneal changes prior to the detection of cornea verticillata on slit-lamp microscopy and may thus be helpful in the early diagnosis of Fabry disease. CLSM does not allow quantitative monitoring of corneal changes in Fabry patients under enzyme-replacement therapy.