dermatome testing is more important assesment in physiotherapy, the above slideshare shows the history of dermatome , testing , dermatome charts , advantage and disadvantage of each chart and clinical conditions

1. DERMATOMES
OF LOWERLIMB
By
S.Christy sopna
M.P.T (OBG)

2. INTRODUCTION
DERMATOME – in greek derma-skin
Tome- section, volume of
Dermatome in 2 ways
▪ Area of skin innervated by a single spinal cord level.
▪ Part of somite that gives rise to the dermis.

3. SOME TYPES OF DERMATOME MAP
MAPS SIGNIFICANCE TESTING
In 1886, SIR WILMOT
HERRINGHAM
Found first segmental
innervation in cadaver
SIR HENRY HEAD Found first dermatome map Clinical observation of referred
pain
Traumatic SCI
Herpes zoster
SHERINGTON Found overlaps in dermatome In rhesus monkey
JAY KEEGAN and FEDERICK
GARETT
Hypoalgesia produced by
compression of a single nerve
root in disc protrusion
Injecting Novocain injection
LEE ET AL Composite from all maps Experimentally reliable
Downs & laporte(2011)

5. SENSORY TESTING
Sensory testing is a common noninvasive method
evaluating nerve function that relies on the knowledge of skin dermatomes and sensory
fields of cutaneous nerves
SUPERFICIAL (EXTEROCEPTIVE) SENSATION
▪ Pain – pin prick
▪ Temperature – 2 test tubes
▪ Light touch – swab of cotton
▪ Pressure – thumb or index finger pressure
▪ Sensory testing typically performed in a distal to proximal sensation.

7. KEY SENSORY POINTS
▪ L1- inguinal ligament
▪ L2- on the anterior-medial thigh, at the midpoint drawn on an imaginary line
connecting the midpoint of the inguinal ligament and the medial femoral condyle
▪ L3- at the medial femoral condyle above the knee
▪ L4 – over the medial malleolus
▪ L5- on the dorsum of foot 3rd metatarsal phalangeal joint.
▪ S1 – on the lateral aspect of the calcaneus
▪ S2- at the midpoint of the popliteal fossa
▪ S3- over the ischial tuberosity or infragluteal fold
▪ S4/S5- in the perianal area less than 1 cm lateral to the mucocutaneous junction

8. WHY KEY SENSORY POINTS?
▪ Show consistent correlation between specific dermatome and
▪ Associated spinal cord nerve level
▪ Even with variation in dermatome maps
▪ Sensory nerves overlap
▪ Key sensory point is consistent
▪ Common area in all dermatome map

9. COMMON SENSORY IMPAIRMENTS
IMPAIRMENT CONDITION
PAIN SENSATION
Analgesia
ALGESIA
complete loss of pain sensitivity.
SCI
Hyperalgesia
Hypalgesia
Increased sensitivity of pain
decreased sensitivity of pain
Causalgia
SENSORY PERVERSION
painful , burning sensation , usually along the
distribution of a nerve
Brachial plexus
injury
Dysesthesia touch sensation experienced as pain Multiple sclerosis
Paresthesia abnormal sensation such as numbness , prickling, or
tingling, without apparent cause
Radiculopathy
TEMPERATURE
Thermanalgesia
THERMESTHESIA
Inability to perceive heat
Thermanesthesia Inability to perceive sensation of heat and cold

10. CLINICAL IMPORTANCE
▪ Diagnosis of radiculopathy
▪ Level of spinal cord injury
▪ Intraoperative monitoring of nerve root and spinal cord function by dermatomal
somatosensory evoked potentials
▪ In anesthesiology, to determine sensory limits of regional anesthesia such as
before cesarian section
▪ In general medicine, dermatomal distribution of referred pain from visceral
diseases.
▪ Pain due to pleurisy, peritonitis, or gallbladder disease - referred to the skin over
the point of the shoulder, halfway down the lateral side of the deltoid muscle. This
is because this area of skin is supplied by the supraclavicular nerves (C3 and C4)
▪ The varicella zoster dormant in dorsal root ganglion,when it become activated
causes vesicular rashes(shingles) in a dermatomal pattern.

11. • Cauda equina syndrome – saddle
anesthesia (S3,S4,S5)
• Meralgia paresthetica – lateral
cutaneous nerve (L2,L3)- altered
sensation,burning
• Hockey player’s syndrome (ilioinguinal
nerve) – L1 dermatome
• Lumbosacral tunnel syndrome – L5
dermatome
• Foot drop –(L4,L5,S1,S2)
• Tarsal tunnel syndrome –(L5,S1)
burning sensation over lateral aspect of
foot

12. SACRAL SPARING
▪ Sacral sparing can be evaluated by 3 tests
▪ Great toe flexor activity
▪ Rectal motor function – bulbocavernosus reflex
▪ Perineal sensation (S3,S4,S5)
▪ If the patient maintains sensation around anal region, this is known as sacral
sparing
▪ S3- ischial tuberosity
▪ S4-S5 – perineal/genital area
▪ The spinothalamic tract is near the corticospinal tract and preservation of the pin-
prick sensation will predict recovery of some of the motor function.

13. DOES RADICULAR PAIN FOLLOW
DERMATOME PATTERN?
Dermatomal Non-dermatomal
Area/nerve root n Percent n Percent
Cervical 20 30.3 46 69.7
Lumbar 37 35.9 66 64.1
Lumbar levels dermatomal Non dermatomal
n percent n percent
L2 2 40.0 3 60.0
L3 4 30.8 9 69.2
L4 8 28.6 20 71.4
L5 8 16.3 41 83.7
S1 24 64.9 13 35.1

14. CONFLICTS IN DERMATOME
▪ No proper evidential dermatome map
▪ Only little evidence on reliability of dermatome
▪ Variability of brachial/lumbosacral plexus -Pre-fixed plexuses(26-48%)
▪ and post-fixed plexus(4%) of population

15. REFERENCES
▪ Downs & Laporte(2011) conflicting dermatome maps:educational and clinical
implications: journal of orthopedic & sport physical therapy 41(6),427-434.
▪ Murphy et al(2009) pain patterns and descriptions in patients with radicular pain:does
the pain necessarily follow a specific dermatome? chiropractic & osteopathy17(9).
▪ Susan o Sullivan “physical rehabilitation”(2014) jaypee publication 6th edition.
▪ Magee “orthopedic physical assessment”(2008) Elsevier publication 6th edition.

16. THANK YOU