Olsen and Canfield divided the scalp into 4 sectors which can be used to estimate the area involved by alopecia or other skin disorder.
Region of the Scalp
Percent of Scalp Area
top of the head
40%
back of the head
24%
left side
18%
right side
18%
Each region can be divided into 4 sectors. For the top and back of the head the sectors are all equal. For the left and right side of the head the sectors are more irregular.
The sides are divided by 2 lines, one vertical just in front of the ear and one horizontal just above the brow. The resultant 4 sectors are:
(1) upper anterior: 5% of scalp area
(2) upper posterior: 4% of scalp area
(3) lower anterior: 4% of scalp area
(4) lower posterior: 5% of scalp area
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