15 Surgical Treatment of Dystonia

10.1055/b-0039-171734

15 Surgical Treatment of Dystonia

John Honeycutt

Abstract

Dystonia was recently defined by the Taskforce on Childhood Movement Disorders as “a movement disorder in which involuntary sustained or intermittent muscle contractions cause twisting and repetitive movements, abnormal postures, or both.” ¹ It is a difficult disorder to diagnose and treat as the presentation of dystonia, overlaps with that of spasticity, chorea and athetosis. This chapter will discuss intrathecal baclofen therapy (ITB) and deep brain stimulation (DBS) for treatment of medically refractory dystonia.

15.1 Patient Selection

Medical management begins with intense physical, occupational and speech therapy and a limited range of medications. Surgical management ensues when the movement disorder is refractory to medical management. As with medical treatment, surgical options are limited. The mainstays are ITB and DBS. DBS has replaced pallidotomy and thalamotomy as a surgical option because of the presence of significant side effects from the bilateral and irreversible lesions. Peripheral denervation procedures are also used for focal cervical dystonia, but botulinum toxin injections and DBS therapy and now predominate.

Purely dystonic patients are most often treated by DBS. Most pediatric patients have a mixture of symptomatic spasticity and dystonia. In these cases, a baclofen pump is first considered because families are concerned about the thought of “brain surgery.” That said, the complication rate of DBS is similar to that which occurs with ITB. The children become dependent on the medication and pumps require frequent refills. There is always a concern of baclofen withdrawal syndrome after refills and pump changes. ² Many patients have both a baclofen pump and DBS, which reduces the required baclofen dose.

Before consideration of baclofen pump insertion, a plastic pump is used to assure that there is adequate space between the iliac crest and rib cage for the implanted pump. If there is insufficient room, the child should be given time to grow. Many of these patients have their pump placement delayed because of their low weight. They are often thin and weight gain is difficult for them because of their movement disorder. After pump placement, they are able to gain weight, perhaps because of the lower caloric consumption when the disorder is controlled.

All DBS evaluations involve a multi-disciplinary team comprised of experienced neurologists, therapists and neurosurgeons. Pre operative testing is done to measure and score performance levels. Priority is given to the improvements of speech and upper extremity function. For most patients, progression from a wheelchair to ambulation is not realistic. Patients and their families may have difficulty understanding this.

For primary dystonia, especially for DYT-1 patients, after failure of medical management DBS is considered. Our series shows that DYT-1 dystonia responds quickly and effectively to DBS. Unfortunately, primary dystonia is encountered less frequently than secondary dystonia Other genetic dystonias can also respond to DBS, but usually not to the same extent. Too often, other medical issues associated with their genetic diseases complicate their lives and medical management. Marks et al., summarized our early comparison of primary (DYT1) versus secondary dystonia DBS outcomes: Both groups responded well, but the primary group continued to improve after 18 months to a greater degree than the secondary group. ³ The results of secondary dystonia treatment is variable (▶ Table 15.1).

**Table 15.1** Summary of demographics and etiology of our 10 year DBS program
Demographics
Average Age(y)	Age Range (y)
13.8	7–29.6
Sex	Male	Female	Total
	57	55	112
Etiology
Primary Dystonia (DYT1)		17
Primary Dystonia Other		19
Secondary Dystonia Cerebral Palsy		38
Secondary Dystonia Other		30
Other (non-dystonia)		8

Enrollment of every DBS patient requires a rigorous consent process approved by the institutional review board in accordance with the current United States FDA Humanitarian Device Exemption status for dystonia. No patient less than seven years old undergoes implantation in our practice. We also encourage participation in PEDiDBS, the international registry of pediatric patients undergoing deep brain stimulation. ²

DBS treatment of primary dystonia is more successful in the long term that for secondary dystonia.

15.2 Pre-operative Preparation-ITB

One of the advantages of ITB is that the patient can undergo an intrathecal baclofen trial. A single CSF dose given by lumbar puncture can show efficacy. However, because of the disorder’s complexity, we do an extended trial using a lumbar catheter that is placed in the OR. Sedation or general anesthesia is used and the patient is admitted to the rehabilitation unit for several days of extensive physical and occupational therapy evaluation. Besides the small surgical risk, a risk of an extended trial is low pressure, spinal headache. This can prevent the patient from standing for long, thus limiting trial effectiveness. Fortunately, this is not a common complication and the headaches resolve soon after the catheter is removed.

Lumbar drain placement is a standard procedure. The catheter tip should be threaded to the therapeutic level. The drain is tunneled laterally to the opposite flank from where the baclofen pump would be placed using the same Tuohy needle used to insert the catheter (▶ Fig. 15.1). If the trial is successful, an intrathecal catheter and the baclofen pump are placed one month later.

**Fig. 15.1** After placement of lumbar drain, the Tuohy needle is measured to maximal tunneling distance **(a)** then used to tunnel the catheter laterally **(b)**

15.2.1 Operative Technique (ITB)

Baclofen pump placement is done under general anesthesia with the patient in the lateral decubitus position. The legs are flexed as much as possible while allowing access to the abdomen. The patient is secured in position with wide tape (▶ Fig. 15.2). Since many patients have gastrostomy buttons or might need them in the future, the majority of pumps are placed subcutaneously in the right abdominal wall. A midline incision is made in lower lumbar spine for the intrathecal catheter insertion. The incision and dissection needs to be large enough to allow the exiting catheter to curve gently towards the pocket. The catheter is placed using a large Tuohy needle from a paramedian trajectory just off midline. This decreases the incidence of catheter kinking between the spinous processes and decreases the risk of catheter fracture. Intraoperative fluoroscopy with the introducing wire still in place is done to confirms the catheter tip location. We use a two-piece catheter. The connecting piece acts as a scarring source to prevent catheter migration

**Fig. 15.2** Patient placed in lateral decubitus position with knees flexed as much as possible still allowing appropriate access to abdominal wall. The incision site is marked.

The baclofen pump is placed submuscular in the abdominal wall. This is because most patients are thin and small. The incision is placed as far away as possible from the pump to help prevent incision breakdown. The pump is placed in the lateral abdominal wall after dissection down to the junction of the external rectus fascia and oblique muscles. The fascia is incised with cautery to expose the deep plane below the rectus and oblique muscles (▶ Fig. 15.3). Epigastric arteries and veins are coagulated and a pocket is created in this space above the internal rectus fascia. Since the transversalis fascia is thin below the arcuate line, dissection below it is avoided. By using this submuscular placement, a 40 ml volume pump can be placed in children as young as three years old. The intrathecal catheter is tunneled from the lumbar incision under the lateral rectus muscle to keep the pump and catheter deep to the incision (▶ Fig. 15.4). Finally, the pump and intrathecal catheter are connected, the pump is positioned in the abdominal wall pocket and secured to the internal fascia with non-absorbable sutures (▶ Fig. 15.5). Patients are kept flat for a day after surgery and then mobilized.

**Fig. 15.3** Dissection carried down to internal fascia with overlying intact epigastric vessels showing the lower rectus muscle mobilized to create a pocket for placement of baclofen pump.

**Fig. 15.4** The intrathecal catheter tunneled under the lateral rectus muscle to keep the catheter protected deep to the incision.

**Fig. 15.5** With submuscular placement of 40 ml baclofen pump, the incision is well protected with little tension on closure and the pump with low profile in small thin patient.

The infusion rate is increased during a two-day postoperative hospitalization. Baclofen pump placement for dystonia is not different from placement for spasticity. However, the catheter is usually placed as high as possible, including occasional placement into the lower cisterna magna. Intraventricular placement can also be done. ⁴ A stim-loc (Medtronic (Minneapolis, MN) skull attachment at the skull may prevent migration.

In thin children, baclofen pumps are placed submuscular to prevent erossion.

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