Evaluation of the cerebello-rubro-thalamic tract after (sub)thalamotomy.

Stereotactic functional neurosurgery is a valid option in the treatment of
medication-refractory debilitating tremor, caused by various conditions such as
Parkinson*s Disease (PD), Multiple Sclerosis (MS), and Essential Tremor (ET).
The goal of the surgery is to suppress the tremor with either a very precise
lesion, so-called (sub)thalamotomy, or with a stimulating electrode in a
particular area of the brain, so-called deep brain stimulation (DBS). The
latter option is nowadays far more popular than lesioning. Important arguments
to prefer DBS are its bilateral application, its adjustability and its
reversible side-effects. On the other hand, DBS is a lifelong therapy with high
costs and other disadvantages. Therefore, in selected cases lesioning may be
preferable over DBS. This project aims to learn more about the therapeutic
mechanism of (sub)thalamotomy.

Various parts of the brain can be lesioned to treat tremor. For this project
the thalamic Ventral InterMediate nucleus (VIM) and the subthalamic Zona
Incerta (ZI) are the targets of interest for this study. Multiple patients
received unilateral stereotactic lesion surgery of one of these nuclei over the
past 25 years in the UMC Groningen. In order to accomplish a successful
neurosurgical intervention it is critical to establish the exact coordinates of
the target. In most cases the nucleus is calculated based on an anatomical
atlas in relation to the anterior commissure - posterior commissure (AC-PC)
line, but it is obvious that this indirect method does not take individual
anatomical variations in account. Recent developments in radiological imaging
have opened the possibility to point out the VIM or ZI directly on high field
strength MRI of the brain. It seems obvious that this new direct method of
targeting can effectuate better clinical results than (sub)thalamotomy did in
the past.

A novel MRI-technique, Diffusion Tensor Imaging (DTI), is based on the
diffusion of water molecules in the brain and can be used to detect
microstructural changes in the white matter. It is also applied to visualize
white matter tracts in the brain. DTI is a cutting edge technique, which makes
it difficult to choose the correct algorithms and settings. Therefore, ongoing
research is performed to evaluate the relevancy and accuracy of DTI.

This evaluation aims to improve the optimal surgical target planning for
thalamotomy, and to optimize the selection process of individual patients for
either DBS or (sub)thalamotomy.

Primary Objective:
• To investigate the difference in localization of the lesioned area in the
brain towards the preoperative assessed target and relate this to registration
and rating of clinical tremor.
• To investigate the role of the dentato-rubro-thalamic tract in lesioning the
VIM or ZI and relate this to registration and rating of clinical tremor.

Secondary Objectives:
• To investigate the patient satisfaction after (sub)thalamotomy.

The design of the project will be partially retrospective (chart and imaging
review) and partially prospective (repeated tremor registration, tremor score,
MRI-DTI and assessment of patient satisfaction).

A cohort of 19 patients that underwent (sub)thalamotomy in the UMC Groningen
will be asked to participate. We expect almost every patient to participate.
Participants will have a clinical evaluation consisting of:

• Tremor registration and video registration, followed by a clinical tremor
rating scale assessment.
• Short questionnaire about patient satisfaction
• Repeat MRI with diffusion weighted imaging (DTI)

All patients had preoperative tremor registration. We want to evaluate whether
the severity of tremor has changed postoperatively. Therefore, patients receive
a postoperative tremor registration and video registration. Video registration
is a common instrument in the department of movement disorders. With use of
video images, tremor severity can be assessed using the Bain & Findley Clinical
Tremor Rating Scale [11]. Since (sub)thalamotomy is done unilaterally, tremor
severity on the lesioned side is related to the contralateral side.
Additionally, patients are asked to fill out a short questionnaire about
patient satisfaction. Subjective tremor severity will be related to objective
tremor severity.

The repeat MRI-DTI is evaluated in the context of the previous imaging. All
patients had preoperative MRI and postoperative MRI and/or CT examinations. The
preoperative MRI was used to determine the target during the surgery.
Postoperative images were obtained to exclude surgical complications (e.g.
hemorrhage). The surgical planning data are saved in the patients charts.
Coordinates of the planned surgical targets are to be related to the position
where targets are actually localized on the follow-up MRI. This is done by
digital merging of the pre- and postoperative MRI. There is extensive
experience in using this software (BrainLab) in the department of neurosurgery.
The DTI data of the cerebello-rubro-thalamic tract on the lesioned side is
related to the surgical target, as well as compared with the tract on the
contralateral side.

Patients will be included from February 2016 untill April 2016. Invitations
will be done telephonically, followed by mailing of study documents. Patients
provide written informed consent on the day of visit.
Patients will get tremor registration and video registration, a short
questionnaire about patient satisfaction on the same day. MRI will be scheduled
on the same day if possible.