While conventional magnetic resonance imaging did not show any sign of involvement in the other components of GMT, DTI demonstrated signal changes in all anatomical components of the GMT. Main DTI findings in GMT of patients with HOD were an increase in radial diffusivity representing demyelination and an increase in axial diffusivity that is reflective of neuronal hypertrophy. DTI parameters can reflect the spatiotemporal evolution of transneuronal degeneration associated with HOD in a manner consistent with the
known pathologic stages of HOD. Hypertrophic Akt inhibitor olivary degeneration (HOD), usually characterized by symptomatic palatal tremor, is a rare and unique type of transneuronal degeneration involving the inferior olivary (IO) nucleus, which occurs secondary to lesions in the components of the Guillain-Mollaret triangle (GMT).1 GMT is composed of the contralateral dentate nucleus, the ipsilateral red nucleus, and the inferior olivary nucleus.1 The ipsilateral central tegmental tract, the contralateral superior cerebellar peduncle, and the inferior cerebellar peduncle form the connecting pathways of these three structures.1 Lesions anywhere on this network may result in HOD. On conventional magnetic resonance imaging (MRI), signal intensity changes in the IO are typically observed about 1 month after lesion HKI-272 nmr onset in the GMT.2–5 IO gradually increases in size, reaching a peak at
about 8.5 months.2 From this stage on, the size remains stable until the 24th month. Thereafter, IO gradually starts to decrease in size. Olivary hyperintensity on T2 weighted images usually persists for years.2 But even at a very late stage conventional MRI rarely demonstrates changes in the central tegmental tract, the superior cerebellar peduncle, the dentate, and red nucleuses, if they are not host of the inciting Urease lesion.6 In contrast, post-mortem studies of HOD reveal that there is
an ongoing dynamic process, starting just after the occurrence of the inciting lesion and extending several years thereafter.4,5 Although conventional MRI is a valuable tool in the diagnosis of HOD, it is not sensitive to dynamic histopathological changes known to occur in these patients. Therefore, we have hypothesized that these complex changes in patients with HOD, including hypertrophic changes in neurons, axonal degeneration, demyelination, and astrocytic hypertrophy, could be investigated by DTI.7 The aim of the study is to assess the pattern of DTI parameters in GMT of patients with HOD, and to relate the directional diffusivities with the known underlying pathologic stages of HOD. Ten patients (3 female and 7 male) who were diagnosed as HOD according to clinical symptoms and MRI findings at our hospital between January 2005 and June 2009 were selected for the study. Mean patient age was 49 (range 16–77). Internal review board of our hospital approved the study, and written informed consent was obtained from all subjects.