What is Neuropathic Pain?
Neuropathic pain is a complex, chronic pain state that usually is accompanied by tissue injury. With neuropathic pain, the nerve fibers themselves may be damaged, dysfunctional, or injured. These damaged nerve fibers send incorrect signals to other pain centers. The impact of nerve fiber injury includes a change in nerve function both at the site of injury and areas around the injury. Neuropathic pain is often described as burning, stabbing, shooting, aching, or like an electric shock.
One example of neuropathic pain is called phantom limb syndrome. This occurs when an arm or a leg has been removed because of illness or injury, but the brain still gets pain messages from the nerves that originally carried impulses from the missing limb. These nerves now misfire and cause pain.
Vast neurosurgery experience by institutions, such as Zurich University, have shown that precise lesions in the thalamus can be effective in the treatment of neuropathic pain.
ExAblate Clinical Results
12 patients suffering from chronic therapy-resistant neuropathic pain, were treated with ExAblate Neuro, using transcraneal MR guided Focused Ultrasound. In 11 patients, precisely localized thermal ablations of 3–4 mm in diameter were produced in the posterior part of the central lateral thalamic nucleus at peak temperatures between 51°C and 64°C with the aid of real-time patient monitoring and MR imaging and MR thermometry guidance. The treated neuropathic pain syndromes had peripheral (5 patients) or central (6 patients) origins and covered all body parts (face, arm, leg, trunk, and hemibody).
Patients experienced mean pain relief of 49% at the 3-month follow-up (9 patients) and 57% at the 1-year follow-up (8 patients). Mean improvement according to the visual analog scale amounted to 42% at 3 months and 41% at 1 year. Six patients experienced immediate and persisting somatosensory improvements. Somatosensory and vestibular clinical manifestations were always observed during sonication time because of ultrasound-based neuronal activation and/or initial therapeutic effects. Quantitative electroencephalography (EEG) showed a significant reduction in EEG spectral overactivities. Thermal ablation sites showed sharply delineated ellipsoidal thermolesions surrounded by short-lived vasogenic edema. Lesion reconstructions (18 lesions in 9 patients) demonstrated targeting precision within a millimeter for all 3 coordinates. There was 1 complication, a bleed in the target with ischemia in the motor thalamus, which led to the introduction of 2 safety measures, that is, the detection of a potential cavitation by a cavitation detector and the maintenance of sonication temperatures below 60°C.
The ExAblate Neuro device has the potential to become a non-invasive tool for highly selective and targeted ablation of deep brain structures. The procedure avoids mechanical brain tissue shift and eliminates the risk of infection. The possibility of applying sonication thermal spots free from trajectory restrictions should allow one to optimize target coverage. The real-time continuous MR imaging and MR thermometry monitoring of targeting accuracy and thermal effects are major factors in optimizing precision, safety, and efficacy in an outpatient context.
(Jeanmonod D, Werner B, Morel A , Michels L, Zadicario E, Schiff G, Martin E. Transcranial MR-guided focused ultrasound: non-invasive central lateral thalamotomy against chronic neuropathic pain. Neurosurgical Focus. Jan 2012. DOI: 10.3171/2011.10.FOCUS11248).
Zurich University has begun the clinical investigation of the feasibility of ExAblate Neuro for treating regions of the thalamus that are the site of neuropathic pain in patients suffering from chronic, therapy resistant pain.
Other Treatment Options for Neuropathic Pain
Some neuropathic pain studies suggest the use of non-steroidal anti-inflammatory drugs, such as Aleve or Motrin, may ease pain. Some people may require a stronger painkiller, such as those containing morphine. Anticonvulsant and antidepressant drugs seem to work in some cases.
If another condition, such as diabetes, is involved, better management of that disorder may alleviate the pain.
In cases that are difficult to treat, a pain specialist may use an invasive or implantable device to effectively manage the pain. Electrical stimulation of the nerves involved in neuropathic pain may significantly control the pain symptoms.
Unfortunately, neuropathic pain often responds poorly to standard pain treatments and occasionally may get worse instead of better over time. For some people, it can lead to serious disability.
E. Martin, D. Jeanmonod et al High Intensity Focused Ultrasound for Non-Invasive
Functional Neurosurgery. Annals of Neurology 2009