What are the guidelines for aspirating cerebrospinal fluid (CSF) and injecting alcohol in a patient over 50 years old with severe, recurrent trigeminal neuralgia and a history of chronic facial pain?

Glycerol Rhizotomy for Trigeminal Neuralgia

For severe, recurrent trigeminal neuralgia in patients over 50 who have failed medical management, glycerol rhizotomy (retrogasserian injection of glycerol after CSF aspiration) is an established ablative procedure, though microvascular decompression remains superior for long-term pain control if the patient has minimal comorbidities. 1, 2

Treatment Algorithm for Refractory Trigeminal Neuralgia

First: Optimize Medical Management

• Carbamazepine remains the gold standard first-line treatment, with oxcarbazepine offering equal efficacy but fewer side effects 1, 3
• In elderly patients over 50, start carbamazepine at lower doses with slower titration due to increased risk of drowsiness, dizziness, and mental confusion 1
• Second-line options include gabapentin (100-200 mg/day initially, up to 900-3600 mg/day), pregabalin (25-50 mg/day initially, up to 150-600 mg/day), lamotrigine, or baclofen (5 mg three times daily, rarely tolerated above 30-40 mg/day in elderly) 1, 3

When to Consider Surgery

• Surgical intervention is indicated when pain intensity increases despite medication optimization OR when side effects become intolerable 1
• Early neurosurgical consultation should occur when initiating treatment to establish a comprehensive surgical plan 1

Surgical Options: Choosing the Right Procedure

Microvascular Decompression (MVD)

• MVD is the only non-ablative procedure and provides the longest pain-free period (70% pain-free at 10 years) 1, 4
• This is the technique of choice for patients with minimal comorbidities and evidence of neurovascular compression on MRI 1, 3
• Risks include 2-4% hearing loss and 0.4% mortality 1

Glycerol Rhizotomy (Retrogasserian Injection)

• The technique involves aspirating 0.2-0.4 ml of CSF from Meckel's cave, then injecting an equal volume of glycerol 5
• Glycerol selectively eliminates pain-conducting components of the trigeminal nerve compound action potential 5
• This procedure is appropriate when patients cannot tolerate MVD due to age/comorbidities, lack neurovascular compression on MRI, or prefer a less invasive option 2, 3
• Results in varying degrees of sensory loss as an ablative procedure 1

Alternative Ablative Procedures

• Balloon compression, radiofrequency thermocoagulation, and Gamma Knife radiosurgery are other ablative options 1, 2
• Gamma Knife delivers 70 Gy to a 4 mm target, with pain relief typically within 3 months; three-quarters achieve complete relief initially, but only half maintain this at 3 years 1
• The most frequent complication of radiosurgery is sensory disturbance, including anaesthesia dolorosa 1

Critical Red Flags in Patients Over 50

• Always rule out giant cell arteritis in patients over 50 with temporal region pain, jaw claudication, or scalp tenderness—this requires urgent ESR/CRP and treatment with systemic steroids 6, 7
• Progressive neuropathic pain or continuous pain (rather than paroxysmal attacks) should prompt MRI to exclude cancer, multiple sclerosis, or structural lesions 6, 8
• Classical trigeminal neuralgia presents with paroxysmal attacks lasting seconds to minutes with mandatory refractory periods between attacks—continuous pain suggests Type 2 TN or alternative diagnoses 8

Common Pitfalls

• Do not confuse trigeminal neuralgia with trigeminal autonomic cephalgias (SUNCT/SUNA), which present with autonomic features like tearing, conjunctival injection, and rhinorrhea, and have up to 200 attacks daily without refractory periods 8
• Glycerol is more neurotoxic than its cryoprotectant properties would suggest, causing greater pain and sensory loss than initially anticipated 5
• Setting realistic expectations is crucial: patients may expect 100% pain relief off all medications for over 5 years after surgery, but outcomes vary significantly by procedure 1