Muscular Tension After Whiplash
This study1 from Sweden examined the role of muscular tension in a group of 22 women with chronic whiplash neck pain. The patients had whiplash symptoms for at least six months, but not longer than 10 years. These women performed a set of maximum isokinetic shoulder flexions on a Cybex II machine, with a maximum of 100 contractions. The investigators recorded surface EMG readings and strength from the exercises, as well as the patients' report of fatigue. The 22 patients were compared to a control group of 27 healthy women with no neck and shoulder pain.
"All but one of the subjects in the control group managed to perform 100 contractions. Only six out of 22 patients were able to perform one hundred contractions. Hence, 16 patients stopped because of severe fatigue." EMG readings indicated that the whiplash patients were unable to relax the muscle tissue between contractions.
The researchers state that they believe that the excess tension may originate from the joints of the cervical spine, rather than the muscle tissue itself. "Mechanical stimulation of joint capsules of the knee and ankles and increased tension in cruciate ligaments have been found to change the activity of the muscle spindle afferents, indicating that ligaments and probably capsules play an important sensory role. The receptors in the ligaments and capsules may contribute to the regulation of muscular stiffness around the knee via reflex actions on the gamma muscle spindle system and thereby to the control of joint stiffness and joint stability. It is likely that receptors in capsules and ligaments play a part in the regulation of muscular stiffness and tension also in the neck."
What does seem to be clear is that muscular tension plays a large role in chronic whiplash pain. Another recent study2 also provides evidence of this.
In this case study, a 28-year-old woman presented to the authors with a 5-year history of headaches after a lateral whiplash injury. Immediately after her accident, the primary clinical finding was localized tenderness in the left trapezius, left scalene, and left posterior cervical paraspinal muscles. Soon the patient reported headaches which would begin with a dull ache in the left trapezius and spread to the whole left side of the face. "Attacks could be precipitated by actively lifting her left arm over her shoulder, carrying heavy objects with her left arm, or excessive neck movement." The headaches were accompanied by autonomic symptoms, i.e., ptosis, nasal congestion, facial numbness, and lacrimation of the left eye. The patient would have these severe headaches at least once per week; they would last for 5 to 6 hours as severe pain, and then be followed for several days of mild or moderate headache. Physiotherapy and medications were ineffective at treating the pain.
The author of the study reported that an injection of botulinum toxin into the localized tender area of the left trapezius muscle resulted in a reduction from 1 headache a week to 1 to 2 headaches per month, and the severity of the attacks was considerably reduced. The headaches returned within 3 to 4½ months after the treatment, necessitating injections of botulinum toxin every three months for the last three years.
In this case, the authors the speculate that the botulinum toxin reduces the muscular overactivity, resulting in a reduction of headache. However, the authors admit, "It appears that some unknown, ongoing, underlying factor persists, and is able to reactivate this local symptomatic area."
At any rate, these two studies are the first to examine closely the role of muscular tension in chronic whiplash pain.
- Fredin Y, Elert J, Britschgi N, et al. A decreased ability to relax between repetitive muscle contractions in patients with chronic symptoms after whiplash trauma of the neck. Journal of Musculoskeletal Pain 1997;5(2):55-70.
- Hobson DE, Gladish DF. Botulinum toxin injection for cervicogenic headache. Headache 1997;37:253-255.
