By B Hilton
Finger flexion, Hoffmann reflex, and Plantar Reflex in DCM
Degenerative cervical myelopathy (DCM) produces a range of symptoms (changes that patients report) and signs (changes that doctors detect through examining a patient). There are several reflexes that occur when the cervical spinal cord is compressed, as it is in DCM. These are: finger flexion, Hoffmann reflex, Plantar reflex (Babinski sign), generalised hyperreflexia, and clonus. Let’s focus on the first three.
Finger flexion - when a doctor taps the base of your fingers with a tendon hammer and your hand moves as if beginning to bring your fingers into a fist
Hoffmann reflex - when the end of your middle finger is flicked downwards, your thumb and first finger flex, as if going to touch each other
Plantar reflex (also known as the Babbinski Reflex) - when a doctor scratches the outside edge of the bottom of your foot and your toes point upwards towards your head
However, these reflexes are not always present in DCM and may be caused by other diseases too. A team of researchers in India investigated how common the reflexes were in DCM and compared this to how common they were in people without DCM.
The team tested the three above reflexes in 32 people with symptoms of DCM and 304 people without DCM. Findings were cross-checked and all participants in the study received an MRI scan of their neck. 24/32 symptomatic patients also had cervical spinal cord compression on their scan. Here’s what they found
Clearly these reflexes are much more common in patients with spinal cord compression and only rarely occur in totally asymptotic patients without spinal cord compression. The team found that when all three reflexes were tested together, if one reflex was positive they could be 92% sure that the patient had DCM. If none of the reflexes were present, they could be 78% sure the patient didn’t have DCM.
What does this mean?
Well we know that detecting early DCM is difficult. What this study shoes is that perhaps the combination of these three tests could be used to assess patients who had been experiencing symptoms consistent with DCM. If even one reflex were positive, they could be >90% sure the patient’s spinal cord could be compressed. If all 3 reflexes were negative, they could be >75% sure that the person’s spinal could wouldn't be compressed. In addition to the patients history, symptoms, and other examination findings, testing these reflexes could offer important insight into who should receive an MRI and potentially see a surgeon scan more urgently and who can likely afford to wait a short while longer.
Of course, it is clear that this reflexes are not perfect. And there are a group of patients with DCM, in whom these reflexes are normal.
1) Tejus MN, Singh V, Ramesh A, Kumar VR, Maurya VP, Madhugiri VS. An evaluation of the finger flexion, Hoffman's and plantar reflexes as markers of cervical spinal cord compression - A comparative clinical study. Clin Neurol Neurosurg. 2015 Jul;134:12-6
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