Adult Neurosurgery — For Physicians · Module

Functional, Pain & Epilepsy

Trigeminal neuralgia, deep brain stimulation, and epilepsy surgery

Reviewed by — Neurosurgeon · Sidra Medicine, Doha · Last updated:

Overview

Functional neurosurgery treats disorders of neural function rather than structural mass lesions, using targeted decompression, ablation, neuromodulation, or resection. This module covers three high-yield areas in adults: trigeminal neuralgia, deep brain stimulation for movement disorders, and surgery for drug-resistant epilepsy.

Trigeminal neuralgia is treated medically first and surgically when refractory; deep brain stimulation is established for advanced Parkinson's disease, tremor, and dystonia; epilepsy surgery offers seizure freedom in drug-resistant focal epilepsy.

Practice rests on randomised and long-term evidence: Barker's long-term microvascular-decompression series, the AAN/EFNS trigeminal-neuralgia parameter, the Deuschl deep-brain-stimulation trial, and the Wiebe and ERSET epilepsy-surgery trials.

References used here

  1. Gronseth G, Cruccu G, Alksne J, Argoff C, Brainin M, Burchiel K, Nurmikko T, Zakrzewska JM. Practice parameter: the diagnostic evaluation and treatment of trigeminal neuralgia (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology and the European Federation of Neurological Societies. Neurology. 2008;71(15):1183-1190.
    Open via DOI Open on PubMed

Trigeminal Neuralgia

Trigeminal neuralgia (tic douloureux) is severe, paroxysmal, electric-shock-like facial pain in the trigeminal distribution, often caused by neurovascular compression of the trigeminal root-entry zone. Medical therapy is first-line, and several surgical options exist for refractory cases.

Epidemiology

Incidence
A common cause of facial pain, more frequent in women and in older adults.
Age peak
Middle-aged and older adults.
Location
Most often the V2 and V3 divisions; classic cases usually involve vascular compression (commonly by the superior cerebellar artery).

Clinical Presentation

  • Brief, paroxysmal, electric-shock or stabbing pain triggered by light touch, chewing, talking, or cold air, with pain-free intervals between attacks.
  • Sensory loss, bilateral involvement, or a young patient should raise suspicion of a secondary (symptomatic) cause such as a tumour or multiple sclerosis.

Imaging

  • MRI, including high-resolution sequences, is used to exclude a secondary cause and to assess neurovascular compression; routine imaging identifies a structural cause in up to about 15% of patients (AAN/EFNS).
  • Findings must be interpreted alongside the clinical features.

Management

Surgery. For medically refractory classic trigeminal neuralgia, options include microvascular decompression (MVD), percutaneous procedures (radiofrequency rhizotomy, balloon compression, glycerol), and stereotactic radiosurgery (gamma knife). MVD addresses the cause, neurovascular compression, and offers the most durable relief: in Barker's long-term series, about 70% of patients were free of pain without medication at 10 years, with low major-complication rates.

Adjuvant therapy. First-line treatment is medical: carbamazepine (Level A) or oxcarbazepine (Level B) per the AAN/EFNS practice parameter, with baclofen or lamotrigine as add-ons.

Considerations. The choice among surgical options balances the durability of MVD against the lower invasiveness of percutaneous or radiosurgical techniques and the patient's fitness for posterior-fossa surgery.

Outcomes

MVD provides the most durable relief; ablative and radiosurgical procedures are effective but carry higher recurrence and more sensory side effects.

By molecular subgroup: Female sex, long symptom duration, and purely venous compression predicted higher recurrence after MVD (Barker).

Clinical Pearls

  • Carbamazepine is first-line, and a clear response also supports the diagnosis.
  • MRI to exclude a secondary cause and to assess neurovascular compression.
  • MVD offers durable relief (about 70% pain-free without medication at 10 years).
  • Sensory loss or bilateral pain suggests symptomatic (secondary) trigeminal neuralgia.

References used here

  1. Barker FG 2nd, Jannetta PJ, Bissonette DJ, Larkins MV, Jho HD. The long-term outcome of microvascular decompression for trigeminal neuralgia. N Engl J Med. 1996;334(17):1077-1083.
    Open via DOI Open on PubMed
  2. Gronseth G, Cruccu G, Alksne J, Argoff C, Brainin M, Burchiel K, Nurmikko T, Zakrzewska JM. Practice parameter: the diagnostic evaluation and treatment of trigeminal neuralgia (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology and the European Federation of Neurological Societies. Neurology. 2008;71(15):1183-1190.
    Open via DOI Open on PubMed
  3. Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th Edition. Thieme, 2023. ISBN: 978-1-68420-504-2.

Deep Brain Stimulation for Movement Disorders

Deep brain stimulation (DBS) delivers adjustable electrical stimulation through implanted electrodes to specific deep nuclei. It is an established therapy for advanced Parkinson's disease, essential tremor, and dystonia.

Epidemiology

Incidence
Considered for advanced Parkinson's disease with motor fluctuations or dyskinesias despite optimised medication, and for medication-refractory essential tremor and dystonia.
Age peak
Typically adults under about 70–75 years with good functional reserve, though selection is individualised.
Location
Targets include the subthalamic nucleus and globus pallidus interna (Parkinson's disease) and the ventral intermediate nucleus of the thalamus (tremor).

Clinical Presentation

  • Ideal Parkinson's candidates have a clear levodopa response but disabling motor fluctuations or dyskinesias; tremor and dystonia are the other main indications.
  • Cognitive and psychiatric screening is essential, because DBS can unmask or worsen cognitive and mood problems in poorly selected patients.

Imaging

  • Stereotactic MRI is used for target planning, sometimes with intra-operative microelectrode recording and test stimulation.
  • Post-operative imaging confirms lead position.

Management

Surgery. DBS electrodes are implanted stereotactically into the target nucleus and connected to an implanted pulse generator. For advanced Parkinson's disease, the randomized trial by Deuschl (2006) showed subthalamic-nucleus stimulation plus medication was more effective than medical management alone for quality of life and motor symptoms at 6 months, although serious adverse events (including a fatal intracerebral haemorrhage) were more frequent with surgery.

Adjuvant therapy. Stimulation parameters and medications are titrated over time within a multidisciplinary movement-disorder service.

Considerations. Careful patient selection (levodopa responsiveness, cognition, and realistic expectations) is the key determinant of benefit; DBS controls symptoms but does not cure the underlying disease.

Outcomes

Well-selected patients gain marked improvement in motor fluctuations, tremor, and quality of life.

By molecular subgroup: Surgical risks include intracranial haemorrhage and hardware infection; benefit depends heavily on candidacy.

Clinical Pearls

  • Patient selection drives outcome: levodopa responsiveness predicts the Parkinson's DBS benefit.
  • STN and GPi are Parkinson's targets; the VIM thalamus is the tremor target.
  • DBS is symptomatic, not curative.
  • Weigh the real surgical risks (haemorrhage, infection) against the benefit (Deuschl, 2006).

References used here

  1. Deuschl G, Schade-Brittinger C, Krack P, Volkmann J, Schäfer H, Bötzel K, et al.; German Parkinson Study Group, Neurostimulation Section. A randomized trial of deep-brain stimulation for Parkinson's disease. N Engl J Med. 2006;355(9):896-908.
    Open via DOI Open on PubMed
  2. Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th Edition. Thieme, 2023. ISBN: 978-1-68420-504-2.
  3. Winn HR (Editor). Youmans and Winn Neurological Surgery. 8th Edition (4-volume set). Elsevier, 2022. ISBN: 978-0-323-66192-8.

Epilepsy Surgery

For drug-resistant focal epilepsy, surgery can achieve seizure freedom that medication cannot. Temporal-lobe epilepsy is the most common and most surgically favourable form.

Epidemiology

Incidence
About one third of epilepsy is drug-resistant; mesial temporal sclerosis is a common, surgically remediable substrate.
Age peak
Adults (and children) with focal epilepsy refractory to medication.
Location
The temporal lobe is the most common site of surgically remediable epilepsy.

Clinical Presentation

  • Drug resistance is defined as failure of adequate trials of two appropriate, tolerated antiseizure medications to achieve sustained seizure freedom.
  • A comprehensive presurgical evaluation (video-EEG, MRI, neuropsychology, and sometimes intracranial monitoring) localises the epileptogenic zone.

Imaging

  • An epilepsy-protocol MRI looks for mesial temporal sclerosis or another epileptogenic lesion; PET, SPECT, and intracranial EEG are added when needed.
  • Concordance of the imaging, EEG, and seizure semiology guides resection.

Management

Surgery. Anteromesial temporal resection (or a lesionectomy or other tailored resection) is offered for well-localised drug-resistant focal epilepsy; alternatives and adjuncts include laser interstitial thermal therapy and neuromodulation (vagus-nerve, responsive, or deep brain stimulation) when resection is not appropriate. The randomized trial by Wiebe (2001) showed surgery for temporal-lobe epilepsy was superior to continued medical therapy (58% vs 8% free of seizures impairing awareness at 1 year), and the ERSET trial (Engel, 2012) supported earlier surgery rather than prolonged medication.

Adjuvant therapy. Antiseizure medications are continued perioperatively and tapered selectively only after sustained seizure freedom.

Considerations. Epilepsy surgery remains underused and is often delayed for many years; early referral of drug-resistant patients to a comprehensive epilepsy centre is recommended.

Outcomes

High rates of seizure freedom follow temporal-lobe surgery in well-selected patients.

By molecular subgroup: Neuropsychological effects, particularly verbal memory in dominant-hemisphere resections, are weighed in the decision.

Clinical Pearls

  • Drug-resistant epilepsy = failure of two appropriate medications → refer early for surgical evaluation.
  • Temporal-lobe surgery beats continued medication (Wiebe, 2001: 58% vs 8% seizure-free at 1 year).
  • Don't wait decades; ERSET (Engel, 2012) supports earlier surgery.
  • Presurgical localisation of the epileptogenic zone is multidisciplinary.

References used here

  1. Wiebe S, Blume WT, Girvin JP, Eliasziw M. A randomized, controlled trial of surgery for temporal-lobe epilepsy. N Engl J Med. 2001;345(5):311-318.
    Open via DOI Open on PubMed
  2. Engel J Jr, McDermott MP, Wiebe S, Langfitt JT, Stern JM, Dewar S, Sperling MR, Gardiner I, Erba G, Fried I, Jacobs M, Vinters HV, Mintzer S, Kieburtz K; Early Randomized Surgical Epilepsy Trial (ERSET) Study Group. Early surgical therapy for drug-resistant temporal lobe epilepsy: a randomized trial. JAMA. 2012;307(9):922-930.
    Open via DOI Open on PubMed
  3. Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th Edition. Thieme, 2023. ISBN: 978-1-68420-504-2.