Gamma knife thalamotomy (GKT) has been used as a therapeutic option for patients with disabling tremor refractory to medications. Impressive improvement of tremor has been reported in the neurosurgical literature, but the reliability of such data has been questioned.
To prospectively evaluate clinical outcomes after GKT for disabling tremor with blinded assessments.
Prospective study with blinded independent neurologic evaluations.
Consecutive patients who underwent unilateral GKT for essential tremor and Parkinson disease tremor at our center. These patients were unwilling or deemed unsuitable candidates for deep brain stimulation or other surgical procedures.
Unilateral GKT and regular follow-up evaluations for up to 30 months, with blinded video evaluations by a movement disorders neurologist.
Clinical outcomes, as measured by the Fahn-Tolosa-Marin Tremor Rating Scale and activities of daily living scores, and incidence of adverse events.
From September 1, 2006, to November 30, 2008, 18 patients underwent unilateral GKT for essential tremor and Parkinson disease tremor at our center. Videos for 14 patients (11 with essential tremor, 3 with Parkinson disease tremor) with at least 6 months' postoperative follow-up were available for analysis (mean [SD] follow-up duration, 19.2 [7.3] months; range, 7-30 months). The Fahn-Tolosa-Marin Tremor Rating Scale activities of daily living scores improved significantly after GKT (P = .03; median and mean change scores, 2.5 and 2.7 points, respectively [range of scale was 0-27]), but there was no significant improvement in other Fahn-Tolosa-Marin Tremor Rating Scale items (P = .53 for resting tremor, P = .24 for postural tremor, P = .62 for action tremor, P = .40 for drawing, P > .99 for pouring water, P = .89 for head tremor). Handwriting and Unified Parkinson's Disease Rating Scale activities of daily living scores tended to improve (P = .07 and .11, respectively). Three patients developed delayed neurologic adverse events.
Overall, we found that GKT provided only modest antitremor efficacy. Of the 2 patients with essential tremor who experienced marked improvement in tremor, 1 subsequently experienced a serious adverse event. Further prospective studies with careful neurologic evaluation of outcomes are necessary before GKT can be recommended for disabling tremor on a routine clinical basis.
"Overall, 14 (8.4%) patients suffered from post-operative complications, which included limited sensory loss contralateral to the side of the procedure, motor impairments, and difficulties with speech. In the same year, Lim et al.  investigated the role of GK thalamotomy in 18 patients with disabling tremor from either ET or Parkinson's disease (PD). The authors utilized the clinical Fahn-Tolosa scale and the United Parkinson's Disease Rating Scale (UPDRS) to assess potential tremor improvements. "
[Show abstract][Hide abstract] ABSTRACT: Medication is the predominant method for the management of patients with movement disorders. However, there is a fraction of patients who experience limited relief from pharmaceuticals or experience bothersome side-effects of the drugs. Deep brain stimulation (DBS) and surgical lesioning of the thalamus and basal ganglia are respected neurosurgical procedures, with valued success rates and a very low incidence of complications. Despite these positive outcomes, DBS and surgical lesioning procedures are contraindicated for some patients. Stereotactic radiosurgery with the Gamma Knife (GK) has been used as a lesioning technique for patients seeking a non-invasive treatment alternative and for medication-intolerable patients, who are unable to undergo DBS or lesioning due to comorbid medical conditions. Tremors of various etiologies are treated using GK thalamotomy, which targets the ventralis intermedius nucleus. GK thalamotomy produces favorable outcomes when treating tremors, with success rates ranging from 80-100%. In contrast, GK pallidotomy targets the internal globus pallidus, and is used in treating bradykinesia, rigidity, and dyskinesia. Although radiosurgery has proven beneficial for tremors, radiosurgical pallidotomy for bradykinesia, rigidity, and dyskinesia remains questionable, with mixed success rates in the literature that ranges from 0-87%. We suggest that GK thalamotomy be offered along with other neurosurgical approaches as a feasible treatment option to patients who prefer the non-invasive nature of radiosurgery and to those who are unqualified candidates for the neurosurgical alternatives. Also, we advise that patients with bradykinesia, rigidity, and dyskinesia be educated about the variability in the literature pertaining to GK pallidotomy before proceeding with treatment.
World Journal of Surgical Oncology 07/2010; 8:61. DOI:10.1186/1477-7819-8-61 · 1.41 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To achieve full transmit diversity for a single user with NT antennas the coherence time of the channel has to be at least NT time-slots long. The same minimum number of slots (or dimensions) guarantees full transmit diversity for every user in a "narrowband" multiuser system in which all users communicate simultaneously and occupy the same bandwidth. However, with an increase in the number of users, an increasing signal-to-noise ratio (SNR) is required of each user to achieve the same error probability as in the single-user case. We showed earlier that this SNR penalty can be alleviated, and even eliminated for sufficiently high SNR, with only a marginal increase of the bandwidth and a judicious design of "spreading matrices" that spread a single-user space-time constellation or (block-) code. In other words, such signaling exploits multiuser diversity and ensures that each user enjoys single-user like performance for sufficiently high SNR. For instance, for NT-transmit antennas per user and a single-user space-time constellation that requires only the minimum time-slots NT, no more than NT+1 slots are required for the common signal space of any number of users. We present here simplified design criteria to obtain the spreading sequences/matrices. We also show that the optimum multiuser receiver can be implemented by the (generalized) sphere decoder of Damen et al. (see IEE Electronics Letters, vol.36, no.2, p.166-167, 2000).
Information Theory, 2002. Proceedings. 2002 IEEE International Symposium on; 01/2002
[Show abstract][Hide abstract] ABSTRACT: Essential tremor is a common movement disorder. Tremor severity and handicap vary widely, but most patients with essential tremor do not receive a diagnosis and hence are never treated. Furthermore, many patients abandon treatment because of side-effects or poor efficacy. A newly developed algorithm, based on the logarithmic relation between tremor amplitude and clinical tremor ratings, can be used to compare the magnitude of effect of available treatments. Drugs with established efficacy (propranolol and primidone) produce a mean tremor reduction of about 50%. Deep brain stimulation (DBS) in the thalamic nucleus ventrointermedius or neighbouring subthalamic structures reduces tremor by about 90%. However, no controlled trials of DBS have been done, and the best target is still uncertain. Better drugs are needed, and controlled trials are required to determine the safety and efficacy of DBS in the nucleus ventrointermedius and neighbouring subthalamic structures.
The Lancet Neurology 02/2011; 10(2):148-61. DOI:10.1016/S1474-4422(10)70322-7 · 21.90 Impact Factor
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