Table 1

Studies describing chronic deep brain stimulation in multiple sclerosis

Study [ref]	n*	Inclusion criteria/sample characteristics	Locus	Follow up	Adverse effects	Tremor suppression†	Effect on daily functions‡
*Number of patients with multiple sclerosis in whom implantation of a chronic stimulator was completed.
†As measured by the percentage of patients showing any sustained improvement (to the end of the follow up period in study) to any degree on any type of tremor scale or instrumentation.
‡As measured by the percentage of patients showing sustained improvement in daily functions such as feeding, holding and manipulating household objects, or subjective quality of life in everyday contexts.
§One patient with multiple sclerosis had bilateral stimulators; data available are for unilateral stimulation (first side).
¶Additional clinical follow up data available. Tremor suppression data are for proximal upper extremity tremor; additional less consistent improvement occurred in distal upper extremity and some improvement occurred in those with lower extremity tremor.
**Mean follow up period was 10 months for the entire sample, including six patients with Parkinson’s disease, 15 with essential tremor, and two with multiple sclerosis; the follow up period for the two patients with multiple sclerosis was not reported separately. In the entire sample, 19 patients underwent either staged or simultaneous VIM implantation, while four received thalamotomy followed by unilateral VIM implantation; it is unclear whether either of the patients with multiple sclerosis was among the minority receiving the combination of thalamotomy and DBS.
††Specific targets within the thalamus were 1 mm posterior to AC-PC midpoint and from 11–15 mm lateral to midline, adjusted in 2 mm increments to the locus where stimulation produced tremor suppression without adverse neurophysiological effects.
MS, multiple sclerosis; UE, upper extremity; VIM, ventrointeromedial nucleus of the thalamus.
Brice and McLellan, 1980⁷	2	Severe disabling tremor; sensation, power, finger movements relatively well preserved; clinically stable for 6 months; failure to respond to drug treatment	Bilateral subthalamic	5–6 months	Not reported separately	100%	100%
Nguyen and Degos, 1993⁸	1	Severe tremor	Unilateral VIM	17 months	None reported	100%	100%
Seigfried and Lippitz, 1994⁹§	9	Not reported	Unilateral VIM	Not reported	None	78%	Not reported
Benabid et al, 1996¹⁰	4	Severe tremor; failure to respond to drug treatment	VIM	3 to ⩾6 months	Microhaematoma (1 MS patient); no other persistent effects; transitory effects not separately reported for MS subsample	50%	Not reported separately
Geny et al,1996¹¹¶	13	Disabling tremor; no relapse within preceding 6 months	Unilateral VIM	3 months	Transitory paresis in lower limb (1 case); dysaesthesiae of <1 min at onset of stimulation (all cases); asthenia (1 case)	69%	92%
Whittle et al, 1998¹²	5	Disabling UE movement disorder; absence of predominantly postural axial tremor or severe neurological dysfunction; ability to locate an effective surgical target	Ventrolateral thalamus	Not reported	Mood disturbances in some	Benefit in some or all patients; no detailed report	Not reported
Hay, 1999¹³	1	Not specifically reported (single case study)	Unilateral thalamus	2 months	None reported	100%	Not reported
Montgomery et al, 1999³	14	Disabling UE tremor without other weakness, sensory, or other problems that would continue to limit functioning; clinically stable for 6 months; no significant speech or swallowing problems; no severe cognitive disability	VIM	<3−12+ months	Intracerebral haematoma (1 case); transient paraesthesiae when stimulator turned on (most cases)	100%	Not reported
Schulder et al, 1999²	5	Disabling UE tremor; failure to respond to drug treatment	Unilateral VIM	⩾6 months	None	100%	60%
Taha et al, 1999¹⁴**	2	Bilateral limb tremor, head tremor, or voice tremor	VIM	∼10 months	Not reported separately for MS patients; no haemorrhage or infarction	100%	Not reported
Schuurman et al, 2000¹⁵	5	Severe UE tremor present at least one year despite drug treatment; age 18 or older; no significant cognitive dysfunction; no contraindications to surgery; no advanced cerebral atrophy; no previous thalamotomy	Unilateral or Bilateral VIM	6 months	Dysarthria, gait/balance disturbance, arm ataxia (3 patients); intracerebral haemorrhage (1 case of entire larger sample)	General improvement, not individually reported	No significant overall improvement; not individually reported
Matsumoto et al, 2001¹⁶	3	Severe UE tremor; clinically definite MS; no significant weakness or sensory loss in the hands; absence of arrhythmic movement disorder; clinically stable for preceding 3 months; no dementia	Unilateral VIM	12 months	None	100%	0%
Hooper et al, 2002^17,⁵††	10	Disabling UE tremor for at least 12 months that had not responded to drug treatment; established diagnosis of MS; no major relapse for 6 months; no severe sensory or motor impairment that would continue to limit functioning; capacity to give informed consent	Unilateral thalamus	12 months	Upper limb paraesthesiae when the DBS was turned on; transitory limb weakness (2 cases), infection at site of IPG necessitating its removal (1 case); intraoperative hypoxic episode (1 case); small thalamocapsular haemorrhages at site of DBS implantation with persistent changes in functioning (2 cases); seizures (2 cases, 1 seizure each)	100%	68 to 78% were same or better at 12 months on two scales; other measures showed no effect
Nandi et al, 2002¹⁸	1	Severe, disabling, progressively worsening UE tremor; gait dysfunction with leg ataxia (single case study)	Unilateral zona incerta	12 months	Worsening of walking and left foot dystonia developed between approximately months 9 and 12	100%	100%