SLAD-R Procedure (Selective Laryngeal Adductor Denervation-Reinnervation)

Definition

Background / Historical Context

• Spasmodic dysphonia was first described by Traube (1871); recognized as a focal dystonia by Fraenkel and Gowers.
• ADSD accounts for ~80% of all laryngeal dystonia cases. ABSD (abductor type) accounts for ~20%.
• Earlier surgical treatment: Dedo's RLN section - initially promising but at 3-year follow-up, only 36% showed persistent improvement and only 3% achieved a normal voice (Aronson & DeSanto).
• SLAD-R was developed by Dr. Gerald Berke at UCLA in the late 1990s, based on in vivo canine studies, to overcome the failures of the Dedo operation.

Rationale / Concept

1. Eliminate dystonic nerve impulses causing adductory spasms.
2. Prevent permanent vocal fold paralysis and paresis.
3. Provide tonic, non-dystonic neural input for muscle bulk maintenance.

Indications

• Confirmed diagnosis of Adductor Spasmodic Dysphonia (ADSD)
• Patients not satisfied with or not responding adequately to botulinum toxin therapy
• Young patients who find repeated injections difficult to maintain
• Patients seeking a more permanent solution

Contraindications / Patient Selection

• Abductor SD (ABSD) - procedure is not appropriate
• Mixed laryngeal dystonia with significant abductor component
• Generalized neurological conditions (Parkinson's, MND, MS, myasthenia gravis) must be excluded before surgery
• Prior failed RLN section (Dedo procedure) - requires careful evaluation

Surgical Technique (Step-by-Step)

• General anesthesia with an EMG-monitoring endotracheal tube (NIM-Response System, Medtronic Xomed) for intraoperative RLN monitoring
• Bed turned 90° from anesthesiologist; surgeon stands at head of bed
• Shoulder roll placed to extend the neck
• Preoperative IV dexamethasone 10 mg + prophylactic antibiotics

• Horizontal neck incision (similar to thyroidectomy)
• Platysma divided, subplatysmal flaps raised
• Strap muscles retracted to expose the thyroid gland and trachea

• The Recurrent Laryngeal Nerve (RLN) is identified as it enters the larynx
• Intraoperative EMG monitoring confirms RLN activity

• The anterior (adductor) branch of the RLN is identified - this supplies the Thyroarytenoid (TA) and Lateral Cricoarytenoid (LCA) muscles
• The adductor branch is sectioned (cut and a segment removed to prevent reattachment)
• The posterior (abductor) branch supplying the Posterior Cricoarytenoid (PCA) muscle is carefully preserved to maintain abductory function

• A branch of the ansa cervicalis nerve (typically the branch to the sternohyoid or omohyoid) is identified and dissected
• This nerve supplies less critical infrahyoid strap muscles

• The harvested ansa cervicalis branch is anastomosed (nerve-to-nerve) to the distal cut end of the adductor RLN branch using microsurgical technique (9-0 or 10-0 nylon suture under microscope)
• This provides tonic, non-dystonic reinnervation to the TA and LCA muscles
• It prevents differential reinnervation by residual dystonic axons

• A conservative LCA myotomy may be performed to reduce the risk of postoperative breathiness (in select cases)
• This was introduced to minimize the complication of permanent breathiness

• Standard layered closure
• Procedure repeated on the contralateral side

Postoperative Voice Changes

Results and Outcomes

• 83% of patients showed significantly improved Vocal Handicap Index-10 (VHI-10) scores at average follow-up of 49 months
• 91% reported their post-surgery voice was more fluent than after Botox therapy
• Initial series (Berke, 1999): 19 of 21 patients had absent to mild voice breaks postoperatively
• Patient satisfaction is high; results are long-lasting (the only surgical treatment for ADSD with demonstrated long-term control)

Complications

• Recurrent symptoms after failure respond to botulinum toxin injections
• Conservative LCA myotomy has minimized the rate of severe permanent breathiness

Comparison with Other Treatments for ADSD

Key Points to Remember (Exam Summary)

1. SLAD-R = Selective Laryngeal Adductor Denervation-Reinnervation
2. For ADSD only (NOT abductor SD)
3. Developed by Gerald Berke, UCLA, late 1990s
4. Denervation: anterior branch of RLN (TA + LCA) - preserving posterior branch (PCA)
5. Reinnervation: ansa cervicalis nerve anastomosed to distal adductor branch
6. Bilateral procedure under EMG-guided intubation
7. Post-op: breathy voice for 3+ months during reinnervation
8. Outcomes: 83-91% improvement, long-lasting
9. Key complication: ~11% recurrence, ~14% permanent breathiness
10. Only surgical treatment with demonstrated long-term symptom control for ADSD