Dermatome and myotome body divisions can now be viewed in real-time on a pain drawing when using Navigate Pain.  A simple click reveals the exact distribution of a patient’s pain report (e.g. aching or sharp pain) relative to classic body divisions.  The new feature also includes simple body region divisions.  Simple divisions, such as those used in epidemiologic studies, include the head, neck, low back, buttocks, thigh and patella.

Clarifying the roles of Dermatomes and Myotomes just got easier

Dermatomes are considerd an area of skin supplied by sensory neurons that arise from a spinal nerve ganglion and myotomes a group of muscles that a single spinal nerve innervates.  The uses and applicability of dermatome and myotome divisions will differ across conditions (e.g. herpes zoster, radicolapathy, nerve root compression) where pain is a major complaint.  Until now, tools to support clinicians and researchers for assessing the utility of dermatome and myotome is limited. 

For researchers this means achieving larger and more powerful data sets is 10 times easier. 

Mapping the distributions of pain can be performed on front, back and side body views. Further, the pain drawings can be collected in the lab, home or in the clinic using the Navigate Pain scheduler.  An average pain drawing requires approxiamately one minute for a new user and 20-30 seconds for future drawing submissions.

An additional benefit is that the detailed body charts (see below) enable a more precise mapping of pain and discomfort.  These precise pain maps can now be viewed relative to the dermatome and myotome body divisions.  An advantage which has only now become available.  Further, the detailed body charts serve as a common reference easing comparison across studies or conditions investigated.  Thus, with every subsequent study the results build upon each other.  

How it Works

Clinicians or researchers can open and view a patients’ submitted pain drawing.  Selecting the upper corner of the pain drawing to view ‘overlays’ superimposes the division of interest. 

A clinician may review the drawing and relation to the divisions prior to his or her first consult.  A researcher may use the feature as part of a big study or a screening questionairre.  The clinician may see a radiating pain pattern down the leg. At this time, one might consider a pathology related to a compressed nerve root.  Upon viewing the qualities it is revealed that patient feels an aching and sharp pain. Both of these qualities are known to associate with compressed nerve roots.  The clinician then toggles the overlay dermatome function ON and sees that the patient mostly shades in a pattern that does not follow the the classic dermatome distribution.  Viewing the information in a glance provides rapid clinical insight on what may or may not be the underlying cause of the pain and discomfort.  Of course further evaluation and functional tests are needed for a differential diagnosis.

One could also consider, for example, radiculopathy or radicular pain, often referred to as a pinched nerve.  A pinched nerve is more closly associated with a dermatomal distribution of numbness and myotomal weakness.  However, Bove et al., (2005) suggests that  referring to myotomal and sclerotomal charts will improve differential diagnoses because radicular pain symptoms are perceived in deep structures rather than on the skin.

Consider why the Dermatome patterns FAIL to match

A number of research studies explored dermatomes as a method to determine the presence and level of nerve root involvement in radiating pain.  It should be clearly noted that not all reports of pain and discomfort match the anatomical nerve root affected.

Not all reports of pain and pins and needles patterns follow a classic dermatomal division.

In a study using selective nerve root blocks, patients with lumbar radiculopathy showed nerve root pain at L4 and L5 commonly deviated from the classic dermatomal pattern.  In contrast, S1 typically followed the classic S1 distribution (Nitta, et al).  This study along with others questions the utility of dermatome patterns in some conditions.  In cases of nerve root compression the dermatomal distribution appears to match between 30-50% of patients (Taylor et al., 2013).

Acknowledging the gap between acute and chronic reports 

To date, many of these studies assessed patients with chornic pain (lasting longer than 6 months).  What remains unknown is what does the clincial picture look like at initial onset?  That is, in an acute pain setting the pain reports may differ substantially.  Thus, there is gap in knowledge between acute and chronic pain reports.  This gap can be addressed by using tools like Navigate Pain in the clinical setting and then applying the features to get answers. 

Capturing initial pain and other discomforts as they unfold are insightful for both the clinician and researcher.

As an example, consider the case of nerve root pain.  Murphey et al., (2009) showed that a patients self-report cannot be used to indicate the level of nerve root compression in lumbar disc prolapse.  But why is this so?  One possibility is that there are other sources of pain occurring at the same time.   The intervertebral disk or dura mater are capable of producing a nociceptive as opposed to neurogenic, pain pattern (Wise et al., 1985).  Other reasons include the possiblity of overlapping dermatomes or an inflammatory (tissue injury) response.  Moreover, persistent and intense pain can also produce an expansion in the patient’s pain report due to changes in the central nervous system; specifically at the spinal level.

The next step…dive deeper and start using the divisions as a means to capture change and understand symptom trajectory. 

References

Nitta H, Tajima T, Sugiyama H, Moriyama A. Study on dermatomes by means of selective spinal nerve block. Spine. 1993;18:1782–6. doi: 10.1097/00007632-199310000-00011. 

Bove GM, Zaheen A, Bajwa ZH. Subjective nature of lower limb radicular pain. J Manipulative Physiol Ther. 2005 Jan;28(1):12-4.

Donald R Murphy, Eric L Hurwitz, Jonathan K Gerrad, and Ronald Cleary. Pain patterns and descriptions in patients with radicular pain: Does the pain necessarily follow a specific dermatome? Chiropr Osteopat. 2009; 17: 9. doi:  10.1186/1746-1340-17-9

Christopher S. Taylor, Andrew J. Coxon , Paul C. Watson, and Charles G. Greenough, Do L5 and S1 Nerve Root Compressions Produce Radicular Pain in a Dermatomal Pattern? Spine 2013 May 20;38(12):995-8. doi: 10.1097/BRS.0b013e318286b7dd.

Weise MD, Garfin SR, Gelberman RH. Lower-extremity sensibility testing in patients with herniated lumbar intervertebral discs. J Bone Joint Surg Am 1985;67:1219–24.