Can Hypersensitivity Be Decreased in Patients of Chronic Whiplash after a Medial Branch Block Procedure

A study 1, in the BMC Musculoskeletal Disorders, was conducted to determine if there was any change in sensory hypersensitivity in patients of chronic whiplash disorders after a medial branch block procedure in the cervical spine. The results showed a decrease in the patient’s pain.

What’s the Context?

It’s common for motor vehicle collision (MVC) to result in cervical spine pain and dysfunction. While many are able to recover (significantly) from neck pain and disability in about six months or even a year, reports show that 32% to 56% of patients continue to suffer.

According to studies, the cervical zygapophyseal joints are known to be a primary source of pain in as many as 60% of people who experience WAD or whiplash associated disorders. Such joints may also be playing a role in peripheral and centrally mediated pain (sensory hypersensitivity).

The Study

The current study was conducted to determine any change in sensory hypersensitivity in WAD grade II patients after a medial brank block (or MBB) procedure in their cervical spine.

This exploratory study utilized a pretest-posttest design. Eighteen participants (3 males, and 15 females) with whiplash associated disorders grade II, and 18 healthy (matches gender breakdown) participants were involved in this study. Take note, patients with chronic WAD and aged 18 to 60 years, who reported neck pain for more than 6 months, and who experienced a minimum of 80% decrease in the said neck pain after an intra-articular zygapophyseal joint block procedure were included.

zygapophyseal joints

The study used a single item Numeric Pain Rating Scale (0-10) for measuring the cervical spine pain intensity of patients before as well as after the MBB procedure.

Quantitative sensory testing (QST), which considered pressure pain thresholds (PPTs’) and cold pain thresholds (CPT’s), was used to measure sensory hypersensitivity. In patients dealing with WAD, the measures were taken at three sites bilaterally, pre and post-MBB. The study used an independent and dependent t-test to determine differences between thresholds.

The Results

The study revealed that, at baseline, the PPT’s were decreased at all three sites in the WAD group. The cervical spine had an increase of cold pain thresholds in the WAD group. Significant increases in PPT’s at all sites was observed in the WAD group (post-MBB), along with a substantial decrease in CPT’s at the cervical spine.

What was Concluded?

The study concluded that chronic WAD patients showed evidence of widespread sensory hypersensitivity in the presence of thermal or mechanical stimuli. Decreased levels of sensory hypersensitivity were observed in the WAD group after the decrease in the primary source of pain caused by the cervical zygapophyseal joints.

However, the study did note that large clinical trials, addressing long-term follow-up interventions targeted at eliminating or reducing the source of cervical pain in WAD patients, were required.

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