View/Open - Scholarly Commons Home

Chapter 2 – Literature Review
controls using PET during postural and rest conditions. The authors
found that at rest the ET group had increased levels of cerebellar blood
flow and showed a bilateral over-activity of the cerebellum during
postural conditions. Increased thalamic activity was also seen in the ET
group during postural conditions. Cerebellar dysfunction was also
pointed to in a multi-voxel magnetic resonance spectroscopy study using
N-acetylaspartate to Choline (NAA/Cho) and N-acetylaspartate to
Creatine (NAA/Cr) ratios (Pagan, et al., 2003). Changes from healthy
NAA/Cho and NAA/Cr ratio levels may indicate presence of neuronal
and/or axonal damage (Bozgeyik, Burakgazi, Sen, & Ogur, 2008). Pagan,
et al. (2003) found reduced NAA/Cr and NAA/Cho ratios of the
cerebellum in 10 ET patients when compared to 10 healthy controls.
Though the authors found this dysfunction they also noted that there
was no neural degeneration in this group of ET patients.
Manifestations of this cerebellar dysfunction include abnormalities in
gait, balance and intention tremor which have been identified in ET
patients (Klebe, et al., 2005; Louis, 2010a). Kronenbuerger et al., (2008)
used conditioned eyeblink response, a model of non-declerative
learning, to evaluate the role of the cerebellum and inferior olive in ET.
The authors compared 33 age-matched participants made up of 11 ET
patients who had undergone DBS, 11 ET with no history of DBS and 11
healthy controls. The results showed that the ET participants with DBS
had improved conditioned responses when compared to non-DBS ET
participants, and theorised that DBS may act on the olivocerebellar
pathway. Kronenbuerger, et al. (2008) also noted that these findings
may support a functional rather than degenerative pathology behind ET.
11