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Spinal Cord Stimulator (SCS) or Dorsal Column Stimulator (DCS) is an implantable medical device used to treat chronic pain of neurologic origin. An electric impulse generated by the device near the dorsal surface of the spinal cord provides a paresthesia ("tingling") sensation that alters the perception of pain by the patient. A surgeon introduces the spinal cord stimulator lead into the epidural space either by percutaneous approach or by surgical laminectomy. A pulse generator or RF receiver is implanted in the abdomen or buttocks. A wire harness connects the lead to the pulse generator.

History

First report of a spinal cord stimulator implantation was in 1967 by Shealy. Studies since then have demonstrated efficacy of SCS in relieving select chronic pain disorders including failed back syndrome, complex regional pain syndrome and peripheral neuropathy.

Surgical Procedure

Complications are generally related to the surgical procedure and can include lead migration, infection, epidural hematoma, paralysis and in extremely rare cases, death. The possibility of lead migration is lessened when placed by laminectomy.

A trial is usually done before the permanent unit is placed. A temporary percutaneous lead is used and is connected to an external pulse generator. The trial is from 3 to 7 days. If the patient has at least 50% improvement in pain during the trial, the patient is considered a candidate for the permanent unit.

Patients with SCS units are not able to have MRI procedures, must avoid areas with high electrical fields, and take caution with anti-theft and metal detector gates. Patients are provided an ID card to allow them to bypass airport security screening gates. Certain other medical procedures must be avoided.

Types of Equipment

There are three types of SCS units:

  • Conventional Implantable Pulse Generator (IPG) consists of a battery and control electronics. When the battery wears out, it is surgically replaced. Battery life is generally 2 to 3 years, but can sometimes be much less.
  • Rechargeable Implantable Pulse Generator (IPG) consists of a rechargeable battery and control electronics. The battery is recharged by an external device worn for a few hours every two to three weeks. Eventually the IPG will need to be replaced, but far less frequently than a conventional IPG. One such device carries a 25 year warrantee in the European Union.
  • Radio Frequency (RF) device consists of an implanted receiver and a transmitter device worn like a cell phone. The transmitter sends RF energy to the receiver which in turn sends stimulation to the lead. RF units are generally used when a lower level of stimulation is needed.

The patient is provided a remote control to turn on and off the stimulator, and depending on the device and the surgeon's preference, allows for limited programming of the stimulation patterns. The surgeon has a programming device that provides a wide range of stimulation settings.

Current and Voltage Configuration

SCS comes in constant current, variable voltage (Advanced Bionics and ANS) or constant voltage, variable current (Medtronic).

Proposed mechanisms of action

Among the proposed mechanism of action of SCS in pain relief include

  • "closing of the gate" by the antidromic activation of large-diameter afferent fibers (see gate-control theory of pain)
  • activation of supraspinal loops relayed by the brain stem or thalamocortical systems providing both ascending and descending inhibition
  • activation of anterior pretectal nucleus which has descending pain inhibitory influces on lower segments
  • suppression of wide-dynamic-range (WDR) neurons responsive to sensory input

Other Uses

SCS units have been used to treat patients with frequent migraines. The leads are implanted in the bilateral suboccipital region.

Trivia

References

Additional references

External Links

Manufacturers

 

This article is licensed under the GNU Free Documentation License. It uses material from the "Spinal Cord Stimulator".

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