UpToDate: Combined Unilateral Posteroventral Pallidotomy and Ventral Intermediate Nucleus Thalamotomy

Combined Unilateral Posteroventral Pallidotomy and Ventral Intermediate Nucleus Thalamotomy

Patients with tremor predominant Parkinson’s disease (PD) achieve more improvement in tremor control after combined unilateral posteroventral pallidotomy and ventral intermediate nucleus thalamotomy 1)2).

Case series

Twenty-four patients with tremor-dominant PD were included in a study of Fayed et al. from the Department of Neurosurgery, Faculty of Medicine, Ain Shams University, CairoEgypt.

Twelve patients received unilateral PVP contralateral to the most affected side. The other 12 patients received simultaneous unilateral PVP and VIM thalamotomy contralateral to the most affected side. Assessment of results in both groups was achieved using both UPDRS “off” motor scores and UPDRS rest tremor subscores.

The mean UPDRS off motor score improved in the pallidotomy group from 61.3 preoperatively to 36.8 at 12 months. In the combined group, it improved from 59.6 to 35.2 at 12 months, with no statistically significant difference between both groups. On the other hand, while the mean tremor subscore in the pallidotomy group improved from a mean of 2.3-0.8, the tremors were abolished in all of the patients in the combined group except for 1 patient who showed slight infrequent tremors at 12 months 3).


Iacono et al. from the Division of Neurosurgery, Loma Linda University Medical Center, combined Vim/VOp junction thalamotomy and PVP in 29 patients with severe tremorrigidity, and bradykinesia. Patients underwent unilateral Vim thalamotomy followed at the same sitting by PVP. The distinct physiological consequences of each procedure were documented by intraoperative electromyography (EMG) and video recording, revealing the effects on both tremor and agonist/antagonist co-contraction. Lack of reciprocal inhibition of antagonistic muscle groups often remained following thalamotomy but was eliminated by subsequent PVP. The complementary therapeutic effects of PVP and Vim thalamotomy may be due to the interruption of different neuronal circuits by the two procedures. The effect of Vim thalamotomy has been attributed to the interruption of the rubrothalamocortical loop. PVP interrupts the outflow of the globus pallidus internus (GPi), which may cause disinhibition of locomotor centers in the mesencephalon and spinal cord. There is no direct interruption of the rubrothalamocortical loop by PVP, explaining why this procedure sometimes exacerbates tremor in certain patients 4).

References

1) , 3)

Fayed ZY, Radwan H, Aziz M, Eid M, Mansour AH, Nosseir M, Anwer H, Elserry T, Abdel Ghany WA. Combined Unilateral Posteroventral Pallidotomy and Ventral Intermediate Nucleus Thalamotomy in Tremor-Dominant Parkinson's Disease versus Posteroventral Pallidotomy Alone: A Prospective Comparative Study. Stereotact Funct Neurosurg. 2018 Sep 18;96(4):1-6. doi: 10.1159/000492229. [Epub ahead of print] PubMed PMID: 30227440.

2) , 4)

Iacono RP, Henderson JM, Lonser RR. Combined stereotactic thalamotomy and posteroventral pallidotomy for Parkinson’s disease. J Image Guid Surg. 1995;1(3):133-40. PubMed PMID: 9079438.

Update: Pallidotomy

Pallidotomy

Indications

Pallidotomy is an alternative to deep brain stimulation for the treatment of the involuntary movements known as dyskinesias which can become a problem in people with Parkinson disease after long-term treatment with levodopa — a condition known as levodopa-induced dyskinesia.
It is also sometimes used in alternative to deep brain stimulation to treat difficult cases of essential tremor.
Unilateral posteroventral pallidotomy can be effective at reducing Parkinsonism, but is associated with impaired language learning (if performed on the dominant hemisphere) or impaired visuospatial contructional ability (if performed on the non-dominant hemisphere). It can also impair executive functions.
Bilateral pallidotomy will not reduce Parkisonistic symptoms but will cause severe apathy and depression along with slurred unintelligable speech, drooling, and pseudobulbar palsy.
Pallidotomy has long been an accepted procedure and the indications for this surgery, in the opinion of the responding centers of a survey of current practice in North America (1996), were rated on a scale of 1 (poor) to 4 (excellent) and demonstrated dyskinesia as the best indication (median = 4); on-off fluctuations, dystonia, rigidity, and bradykinesia as good indications (median = 3); and freezing, tremor and gait disturbance as fair indications (median = 2). Most centers used MRI alone (50%) or in combination with CT scan (n = 6) or ventriculopathy (n = 5) to localize the target. The median values of pallidal coordinates were: 2 mm anterior to the midcommissural point 21 mm lateral to the midsagittal plane and 5 mm below the intercommissural line. Microrecording was performed by half of the centers (n = 14) and half of the remaining centers were considering starting it (n = 7). Main criteria used to define the target included the firing pattern of spontaneous neuronal discharges (n = 13) and the response to joint movement (n = 10). Most centers performed motor (n = 26) and visual (n = 23) macrostimulation. Twenty four centers performed test lesions using median values of 55 degrees C temperatures for 30 s. Final lesions consisted of 3 permanent lesions placed 2 mm apart, each lesion created with median values of 75 degrees C temperatures for 1 minute. Median hospital stay was 2 days 1).
1) Favre J, Taha JM, Nguyen TT, Gildenberg PL, Burchiel KJ. Pallidotomy: a survey of current practice in North America. Neurosurgery. 1996 Oct;39(4):883-90; discussion 890-2. PubMed PMID: 8880789.
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