Deep brain stimulation is used in a variety of clinical settings, predominantly in patients with treatment-refractory movement disorders. Although effective, its exact mode of function continues to be poorly understood ².  

Careful patient selection and target selection are essential if the procedure is to have good efficacy.

Indications

• Parkinson disease

  • subthalamic nucleus ¹

  • globus pallidus internus

  • ventral intermediate thalamic nucleus

  • pedunculopontine nucleus ¹⁶

• essential tremor

  • ventral intermediate thalamic nucleus ^2,12

  • posterior subthalamic area (caudal zona incerta) ¹²

• other tremor syndromes (e.g. Holmes tremor)

  • ventral intermediate thalamic nucleus ¹⁷

• dystonia syndromes (e.g. DYT1 dystonia, cervical dystonia) ^4,10

  • globus pallidus internus

• Tourette syndrome ⁹

  • thalamus: centromedian nucleus–nucleus ventrooralis internus complex, centromedian nucleus–parafascicular complex

  • globus pallidus internus: posteroventrolateral, anteromedial portion

• epilepsy ^11,13-15

  • thalamic anterior nucleus

  • thalamic centromedian nucleus

  • bilateral hippocampus

• cluster headaches ⁶

  • hypothalamus

• chronic pain ⁵

  • thalamus

  • periaqueductal grey matter

• neuropsychiatric disorders: largely experimental ⁴

  • major depressive disorder

    • white-matter tracts adjacent to cingulate gyrus

    • nucleus accumbens

    • medial forebrain bundle ⁸

  • obsessive-compulsive disorder

    • anterior limb of internal capsule

    • subthalamic nucleus

    • striatum

Procedure

A stereotactic frame is applied and imaging obtained to enable accurate target selection. With the aid of multiplanar reformats and operative stereotaxis, a burr hole is made for each probe and the electrode passed to the desired target, avoiding the lateral ventricles, vessels and sulci. Intraoperative stimulation is then performed to ensure adequate positioning. Leads are tunnelled under the skin and the internal pulse generator implanted in a similar location to a pacemaker.

Complications

Complications can be immediate or delayed ¹²: 

• immediate

  • haemorrhage (~1.5%)

    • can be secondary to venous infarction

  • infarction

  • local brain parenchymal oedema (~3%)

    • unilateral or bilateral

    • 4-120 days postoperatively

    • asymptomatic or present with headache, seizure

• delayed

  • infection (~12.5%): most commonly the pulse generator pocket

  • lead fracture (~10%)

Side effects predominantly relate to the stimulation itself, which may lead to dysarthria, disequilibrium, motor disturbances and paraesthesia. These symptoms vary with the location of the probes.