The Norwood Scale
Patterned hair loss or androgenetic alopecia is the most common cause of baldness in both genders. By the time they reach the age of 50 years, nearly half of all men will have some degree of hair loss attributable to male-pattern baldness.
A classification system to grade the extent of hair loss is helpful in diagnosis, monitoring, and deciding an appropriate treatment approach.
Various such classification schemes have been proposed over the years. The majority of them are focused on male-pattern baldness as the pattern of hair loss is predictable and follows a natural course of progression. The most widely used among them is the Norwood scale.
What is the Norwood Scale?
Norwood scale was first introduced by Dr. O’ Tar Norwood in 1975, a prominent US-based dermatologist and hair transplant surgeon.
After studying the pattern of hair loss in 1000 Caucasian men, he noticed that thinning of hair starts at the temples as well as the vertex and the two bald areas gradually enlarge to encompass the whole scalp. This grading scheme is a modified version of Hamilton’s scale, which was proposed by Dr. Hamilton in 1951, and therefore it is sometimes referred to as the Norwood-Hamilton scale. Norwood simplified the grading process by reducing the number of grades from 8 to 7. He also described ‘type A variants’ for types II, III, IV, and V. Dr. Norwood died in August 2020 at the age of 89, but his legacy remains in the form of the Norwood scale.
Apart from Hamilton, several other hair loss classification systems were defined before the introduction of the Norwood scale, including Beek classification (1950), Ogata (1953), and Setty (1970). Other classification schemes for male pattern baldness were introduced after the Norwood scale as well, such as Bouhanna (1976), Blanchard (1984), and Koo (2000).
The most recent one is the Basic and Specific classification system (BASP) introduced in 2007 by Lee, though the Norwood scale remains the most widely known and used system to date. It is one of the most detailed systems with a total of 12 different categories when the type A variants are considered. This allows more precise categorization than the Hamilton scale, which it replaces, and is helpful for hair transplant surgeons to devise appropriate surgical approaches.
Despite its numerous advantages and widespread usage, the Norwood scale has its drawbacks. Being excessively detailed, it is a relatively complicated classification which makes it prone to inter-observer variability. Nevertheless, its near-universal adoption makes it the best-suited grading system for male-pattern baldness.
The 7 stages of hair loss
Hair loss is categorized into 7 types on the Norwood scale, each designated by a Roman numeral from I to VII. The grading starts from minimal to no hair loss, indicated by type I, and each subsequent grade denotes progressively extending baldness, with type VII being the most severe form characterized by complete baldness at the vertex.
Type 1: No hair loss or recession of the hairline
Norwood Type I describes a hair pattern with no discernable hair loss and minimal to no recession of the hairline along the frontotemporal border. It is common in men in their teens and twenties. No treatment is required as there is no significant hair loss.
Type 2: Mild hairline recession
Norwood type II represents early hair loss which is mild but thinning of hair is apparent at the frontotemporal region. Hairline recession at the temples leaves a bare triangular area on either side. If a line is drawn between the two ear openings passing along the frontal scalp, the recession at temporal regions usually stops at about 2 cm in front of the line. Thinning of hair and recession occurs at the mid-frontal hairline too but the depth is much less than that at the temples. This gives the hair a backward sloping angle when viewed from the side. The vertex or crown remains covered by hair.
Type 3: Deep recession of the hairline with or without hair loss at the vertex
Norwood described type III hair loss as the minimal extent of hair loss sufficient to represent baldness. The recession at frontotemporal areas is deeper than in type II and may reach the mid-coronal line but does not extend beyond it. The mid-coronal line is an imaginary vertical line that cuts the body into equal front (anterior) and back (posterior) halves. A variant of type III is called the type III vertex which is discussed below in the section “other variants in the Norwood scale”. Treatment options for type III hair loss include medications (finasteride, minoxidil, etc.) and hair transplant.
Type 4: Deeply recessed hairline and vertex baldness
At this stage, the hairline recession is deeper than in type III and there is an area of hair loss at the vertex too. The two bald areas are separated by a strand of relatively dense hair which extends around the scalp. Type IV hair loss is differentiated from type III vertex by the fact that frontal hairline recession is less pronounced in the latter. This type of hair loss significantly alters the appearance of a person and requires treatment. Medications may be able to arrest further hair loss and grow back some hair but full restoration is unlikely. Hair transplant surgery is an appropriate option as enough hairy patches remain on the scalp to serve as a suitable donor area.
Type 5: Only a narrow band of hair separates the vertex and temples
The hair loss is more extensive both at the frontotemporal area and the vertex. A thin, sparsely-haired band still separates the two areas but both the bald spots are significantly larger. The sides and back of the scalp are populated by relatively dense hair. The hair loss is extensive and treatment options are, therefore, limited. Medications are unlikely to result in significant hair restoration but may halt further hair loss. Hair transplant surgery is useful to achieve a fuller scalp but remaining scalp hair may not be sufficient to provide a sufficient harvest and body hair may have to be used.
Type 6: Temple hair loss joins the vertex area
Type VI is the second last stage of male-pattern hair loss on the Norwood scale. The frontotemporal hairline recession extends backward to meet the bald area at the vertex. The bridge of hair that crosses the crown is either completely lost or only sparse hair remains. In addition, there is an extension of the hair loss towards the sides and to the back. This is an advanced stage of baldness and medical therapy is unlikely to be effective. Hair transplant surgery is viable given enough hair remains on the scalp that can be harvested for implantation.
Type 7: Only a band of hair around the sides of the head exists
The last category in the Norwood classification, type VII hair loss denotes complete baldness. The frontal areas and vertex are devoid of hair with the only hair remaining on the scalp confined to a horseshoe-shaped band on the back of the head, extending forward only as far as the ears. The hair that remains is less dense and thin. The hair at the back of the head is thought to be resistant to the effects of DHT, the hormone responsible for male-pattern baldness. Stages above type V represent advanced alopecia and treatment is difficult. If a hair transplant is considered, body hair may need to be harvested.
The scale from 1-7 in pictures
The pictures presented here show the different stages of hair loss as per the Norwood scale. Type I: no noticeable hair loss or hairline recession. Type II: mild recession of the hairline at the temples. Type III: The hairline recedes deeper than type II. Type IV: hairline recedes significantly with thinning of hair at the vertex. Type V: the bald patches at the front and the vertex are separated by a bridge of less dense hair. Type VI: the bald patches at the front and vertex coalesce. Type VII: complete baldness with only a hair strip remaining at the back.
Female version – The Ludwig Scale
The Norwood scale is used exclusively for male-pattern baldness. The Ludwig scale, developed by Eric Ludwig in 1977, is an alternative scale used for female-pattern hair loss.
It should be noted that hair loss in female patients with male-pattern hair loss should be categorized according to the Norwood scale. The Ludwig scale focuses more on hair loss at the vertex/crown area, in line with the predominant pattern of hair loss in female-pattern baldness. Although widely used, this scale does not take into account progressive frontal hair loss. After observing patterns of hair loss in more than 400 female patients, Ludwig described three progressive grades of hair loss.
- Grade I: This early-stage hair loss includes minimal but perceptible thinning of hair on the crown of the head without a significant recession of the hairline.
- Grade II: There is considerable thinning of the hair over the vertex area. Patients may notice widening of the part and more of the scalp becoming visible in between the sparser hair.
- Grade III: This is the most severe type of hair loss with a large area of the vertical scalp being devoid of hair.
Apart from the Ludwig scale, other grading schemes have been described for female-pattern hair loss including by Savin (1992), Olsen (1994), and Sinclair (2004). In 2007 a new classification system, the basic and specific system was proposed which applies both to male and female pattern baldness.
Other variants in the scale
Apart from the seven main types, 5 “type A” variants have been defined in the Norwood scale. The type A variants describe a pattern of hair loss solely characterized by the recession of the frontal hairline and are defined by two major and two minor features.
The major features include recession of the frontal hairline to the rear without leaving an island of hair in the mid-frontal region and no simultaneous development of a bald area on the vertex. The minor features are the persistence of sparse hair scattered in the area of hair loss and a wider and high-reaching horseshoe-shaped area on the back and sides. The following type A variants were described by Norwood:
- Type IIA: The hairline recession does not extend beyond a point 2 cm in front of the level of the external ear opening.
- Type IIIA: The hairline has receded to a point between the limit of Type IIA and the level of the external ear opening.
- Type IVA: The hairline has receded beyond the level of external ear opening but has not reached the vertex.
- Type VA: The area of hair loss includes the vertex
As mentioned above, type III also has a vertex variant (type III vertex), in which there is a bald patch at the vertex in addition to the frontal hairline recession.
Norwood scale in relation to hair transplants
From a practical standpoint, mapping the area of hair loss using the Norwood scale is usually the first step when considering a patient for hair transplant surgery.
Grading of hair loss is useful regarding hair transplant surgery on two accounts. First, the severity of alopecia determines the indication for surgery and the appropriate procedure to be used. Secondly, the number of grafts to be used and the selection of the donor area(s) is dependent on the extent of hair loss and the quality and quantity of the remaining hair.
Medical therapy can be considered in cases of mild to moderate hair loss (Norwood type I-III), where preservation of the remaining hair by halting the hair loss process may be sufficient. In Norwood II/III hair loss injection of platelet-rich plasma (PRP) may result in preventing further hair loss and even promote hair growth.
Hair transplant using FUT or FUE will likely be a more suitable option in patients with relatively advanced hair loss (Norwood IV/V). Hair transplant is also one of the few viable options for patients with severe hair loss (Norwood VI/VII) though the lack of availability of a suitable donor area makes the procedure challenging.
How many grafts approximately do I need?
The number of grafts required for a hair transplant surgery depends on the extent of baldness. An estimation of the number of grafts required is important before transplant as most clinics have their charges set at per unit graft.
While there is likely to be a considerable variation between two patients categorized with the same Norwood scale, a general approximation can be made using the scale. A Norwood type II hairline recession, for example, will require 500 to 800 grafts for satisfactory results. A rough guide to the number of grafts required is given here:
- Norwood II: 500 – 800 grafts. In the UK, the cost of such a transplant using the FUE (follicle unit extraction) procedure will range from £1000 to £4000.
- Norwood III: On average, 1000-1400 grafts will be required.
- Norwood IV: This will likely require 1200-1600 for the frontal hairline and another 600-800 for the crown, making a total of 1800 – 2400 grafts
- Norwood V: This will require 1800-2000 for the frontal hairline and 1000-1500 for the crown.
- Norwood VI & VII: 4000-5000 grafts will likely be required for the advanced types of hair loss.