Regarding Dermatomes.....

A 55-year-old woman complains of neck and right arm pain for the past two months. The pain is often triggered by flexing her neck. Her past medical history includes osteoarthritis of her knee, obesity and depression.
On examination there is no obvious muscle atrophy or weakness of the right arm. There is however some sensory loss over the middle finger and palm of the hand.
Which nerve root is most likely to be affected by the impingement?
A. C4
B. C5
C. C6
D. C7
E. C8

Answer:
D. C7

Discussion:
Dermatomes:
Below is a list of  the major dermatome landmarks:

C2 :               Posterior half of the skull (cap)
C3 :               High turtleneck shirt
C4 :               Low-collar shirt
C5, C6 :        Thumb + index finger (Make a 6 with your left hand by touching the tip of the thumb &                      index finger together - C6)
C7  :              Middle finger + palm of hand
C8 :               Ring + little finger
T4 :               Nipples (T4 at the Teat Pore)
T5 :               Inframammary fold
T7  :              Xiphoid process
T10 :             Umbilicus  9BellybuT-TEN )
L1 :               Inguinal ligament  (L for ligament, 1 for 1nguinal)
L4 :               Knee caps ( Down on aLL fours - L4)
L5 :               Big toe, dorsum of foot (except lateral aspect) ( L5 = Largest of the 5 toes)
S1 :                Lateral foot, small toe (S1 = the smallest one )
S2, S3 :         Genitalia