Ataxia in Essential Tremor: Describing the Differences Between Disease Process and Treatment Effect

Objectives: In recent years, there has been a growing amount of evidence tying Essential
Tremor (ET) to cerebellar dysfunction. This has been clinically observed, demonstrated
through specific gait measures of ataxia (often involving tandem gait), and confirmed through
Positron emission tomography (PET) imaging. Deep Brain stimulation for ET has become a widely
utilized therapeutic intervention for patients, and the bilateral thalamic ventralis
intermedius (VIM) is most commonly implanted. However, it has been noted that in some
patients gait ataxia significantly worsens post-op. This initially was thought to be a result
of disease progression, but recent studies have in fact shown that this is a DBS related
phenomenon.

Methods: Participants will have two visits to either the Portland VA or Oregon Health &
Science University (OHSU). At each visit, several assessments of balance, tremor, gait and
balance, and DBS settings will be made. The gait and balance assessments will be performed by
a unblinded and a blinded rater.

Inclusion Criteria:

- Essential Tremor diagnosis at least 3 years duration

- Absence of other neurological signes (such as dystonia, ataxia, or Parkinsonism)

- Patients must be able to walk 2 minutes unassisted.

- Patients must be able to understand and consent to be in the study.

Exclusion Criteria:

- Patients who have had changes in DBS settings within the last 3 months.

- Patients who have had no initial improvement or response to DBS.

- ET medication changes in the last month.

- Actively abusing alcohol.

- A neurologic diagnosis other than ET that in the investigator's opinion could affect
gait and/or balance.

- Atypical tremor disorder including by not limited to tremor due to multiple sclerosis,
medication-induced tremor, Parkinson's disease, or parkinsonian syndrome.

- Dementia