Trichodynia

Trichodynia also called “hair pain”, scalp dysaesthesia or cutaneous dysesthesia syndrome, is defined as a painful sensation within scalp hair, which becomes more intense when hairs are touched ¹. The term “trichodynia” has also been proposed for discomfort, pain or paresthesia (burning, or stinging) of the scalp related to diffuse hair loss (alopecia) ². Sulzberger et al. ³ reported that trichodynia may also be circumscribed (“spotty”). The pain occurs with no pathological findings, and is usually considered a type of somatoform disorder ⁴. Trichodynia should be differentiated from scalp dysesthesia, which refers to situation when the symptoms reported by the patient are localized on the scalp skin, while in trichodynia patients indicate that the pain or burning is solely limited to the hair itself ¹. Many patients with trichodynia present other psychiatric symptoms, including depression, obsessive-compulsive or anxiety disorders. The cause of trichodynia is not known, but it is suggested to be of multifactorial origin ⁵.

Trichodynia has been found that 34% of female patients with hair loss complained of this phenomenon ⁶. In a recent survey, Grimalt et al. ⁷ showed that 14% of their diffuse alopecia patients reported trichodynia. Complaints such as pain and burning of the scalp in patients with diffuse hair loss (alopecia) were described in the earlier dermatology literature ⁸. Both such studies and clinical observations have led to the idea that the diffuse alopecia or telogen effluvium and trichodynia are related. By definition, telogen effluvium is a nonscarring and diffuse hair loss from the scalp that occurs a few months after a triggering event ².

Although dealing with trichodynia can be distressing and literature support is weak, there are a number of treatments available.

Trichodynia causes

The cause of trichodynia is not known, but it is suggested to be of multifactorial origin ⁹. It is commonly believed that trichodynia correlates with emotional upset ¹⁰. Trichodynia is almost exclusive of patients with active telogen effluvium, was described in the alopecia areata (14% of cases), folliculitis decalvans, or frontal fibrosing alopecia (hair loss) ¹¹.

The underlying mechanisms creating the pain are not clear, though it has been proposed that it is probably multi-etiological. The most accepted hypotheses are increased expression of the neuropeptide substance P, underlying psychiatric disorders, nutritional deficiencies, and perifollicular inflammation ¹². Substance P is involved in pain perception by the nerve endings, and changes in the production and activity of substance P around the hair follicles may be responsible for the pain and burning sensation ¹³. Hair follicles are innervated by unmyelinated neural plexuses located around the hair follicle stem cells. These nerve fibers contain neuropeptides including substance P and calcitonin gene-related peptide (CGRP). These neuropeptides play an important role in the regulation of hair growth and are associated with the neurogenic inflammatory response. Perifollicular substance P is also involved in the regulation of hair growth ¹⁴. An imbalance in the tonic release of neuropeptides may result in inhibition of hair growth. Cutrer et al. ¹⁵ hypothesized that chronic activation of the c-fibers, in addition to mediating inflammatory pain and follicular injury, might reduce substance P and CGRP concentrations resulting in altered peribulbar antigen presentation and inhibition of further hair growth.

Another explanation may be an underlying psychiatric disorder. It has been found that 76% of the people who had trichodynia had psychopathic signs versus 20% in the control group, supporting this idea. Researchers have observed and speculated that there is a connection between psychopathologic findings (such as anxiety) and trichodynia ¹⁶. In 2006 Gupta and Gupta ¹⁷ found that numbness and pain are common symptoms of somatoform dissociation or conversion reaction. Kivanç et al. ¹⁸ found that trichodynia was associated with depression in the telogen alopecia group and with obsessive-compulsive personality disorder in the androgenic alopecia group. However, this idea is controversial. Although increased rates of psychiatric problems have been reported in patients with trichodynia, Ozturk et al. ¹⁹ found no association between trichodynia and depression or anxiety. In this study the patients with telogen alopecia were consisting the control group, and they could have the opportunity to evaluate only the trichodynia patients ¹⁹.

Neuropathic pain can also be associated with nutritional deficiencies (Iron [Fe], vitamin B12, ferritin, zinc, vitamin D, vitamin E). Nutritional factors affect the hair directly, and dietary supplements containing B complex vitamins can influence hair growth ¹⁹. Nutritional deficiencies have been reported in other cutaneous dysesthesia syndromes. For example, glossodynia is characterized by a burning sensation of the tongue and oral mucosa. Menopause, psychogenic disorders, and nutritional factors have also been suggested to cause this phenomenon ²⁰. However, evidence level is very low to confirm this nutritional hypothesis for trichodynia patients ²¹.

Other dermatological conditions causing scalp pain

Scalp pain can occur with cicatricial alopecia that can be caused by a fungus infection or autoimmune conditions such as cutaneous lupus and lichen planopilaris. Folliculitis decalvans and dissecting cellulitis are forms of primary neutrophilic scarring alopecia that are characterized clinically by chronic suppurative folliculitis and often associated with pruritus or even pain. The inflammatory cells may irritate nerve endings leading to a burning or painful sensation. Hair dye-related dermatitis may also cause burning sensations.

There are also painful tumoral lesions of the skin and subcutaneous tissue. These lesions can be found anywhere in the peripheral nerve tissue. They have a propensity for developing on the skin and subcutaneous tissue, as well as in oral and pharyngeal locations. An old acronym may help us to remember them. LEND AN EGG tumors (leiomyoma, eccrine spiradenoma, neuroma, dermatofibroma, angiolipoma, neurilemmoma, endometrioma, glomus tumor, and granular cell tumors) must always be considered when there is a tumoral lesion associated with pain ²².

Trichodynia symptoms

Trichodynia is defined as a painful sensation in the skin of the scalp or the hair itself and becomes more intense when hairs are touched. Trichodynia presents with complaints such as tenderness, pain, burning, itching, stinging, and diffuse hair loss ⁷.

Trichodynia diagnosis

Trichodynia diagnosis is based on clinical suspicion. A comprehensive history and examination are needed to identify any underlying cause and excluded a primary dermatological disease ²³. If the patient reports headache or temporal pain by palpation, tension headaches or temporal arteritis should be evaluated first.

Diagnostic tests may include:

• Trichoscopy. Trichoscopy is a non-invasive technique based on dermoscopic evaluation of the scalp hair, which allows a 10× magnification. Recently, besides manual trichoscopy, videodermoscopy has gained importance. It is a non-invasive diagnostic tool, initially used to evaluate and monitor pigmented skin lesions, that has proven to be useful in the scalp diseases. A magnification ranging from 20× to 70× allows the in vivo visualization of scalp epidermis, follicles, hair shafts and vascular patterns. Moreover, images can be stored to get a global photographic assessment that can be used in further controls to evaluate the hair growth ²⁴.
• Phototrichogram. This technique involves trimming the hair of a 2 square cm area of scalp, pictures of the same area taken on different days, and then compared in hair density, hair growth, and rate of shedding. Since only anagen hair would elongate it helps in the assessment of the ratio of anagen:telogen hair. A TrichoScan is a fully computerized phototrichogram ²⁵. A TrichoScan is a simpler, noninvasive, reproducible, and more sensitive than a classical trichogram and very useful in the diagnosis of hair loss ²⁵.
• Trichogram is a plucking of hair in a defined area (40-60 hair). Cases of telogen effluvium show a significant reduction of the anagen:telogen ratio. More than 25% of hair are found to be in the telogen phase in the case of telogen effluvium ²⁶.
• Scalp biopsy. Scalp biopsy can be useful when the clinical evaluation does not provide a definitive diagnosis, and cicatricial alopecias or alopecia areata are suspected.
• Blood tests.
  • A hyperandrogenic state should be considered in women with female androgenetic alopecia associated with signs of androgen excess (e.g. hirsutism, irregular menses, acne, hyperprolactinemia, acanthosis nigricans); while it is not indicated in all women with female androgenetic alopecia ²⁷. Free androgen index test (FAI = total testosterone [nmol L−1] × 100/sex hormone binding globulin [SHBG]) and prolactin as screening parameters for ovarian hyperandrogenism and dehydroepiandrosterone sulfate (DHEA) and 17-hydroxyprogesterone (17-OH-P) as screening parameters for androgen-producing tumors and adrenal congenital hyperplasia are recommended ²⁸. Note that testing of androgen levels should be done during the follicular phase, between the fourth and the seventh day of the cycle, and that oral contraceptives should be discontinued for at least 2 months prior to this testing ²⁹.
  • Measurements of blood iron, ferritin, vitamin D, zinc and thyroid profile may be useful to assess and treat other conditions that may impact on hair regrowth in female androgenetic alopecia ²⁷.
  • Serology: antinuclear antibody (ANA), antineutrophil cytoplasmic antibodies (ANCA), C-reactive protein (CRP)
  • Ovarian and adrenal ultrasound could be prescribed to rule out the presence of ovarian cysts and androgen-producing tumours or adrenal congenital hyperplasia ²⁸. Depending on the results, further investigations may be needed and an interdisciplinary approach involving gynaecologists, endocrinologists and dermatologists may be required ²⁸.

Trichodynia treatment

Although dealing with trichodynia can be distressing and literature support is weak, there are a number of treatments available. L-Cystine-containing oral preparations, topical corticosteroids (both high potency and low), and anti-inflammatory drugs have been advocated ². Inhibitors of substance P can also be tried. Cannabinoids, for example, have been demonstrated to inhibit substance P ³⁰. Capsaicin cream has been used because it blocks substance P when applied to the hair follicles. On the basis of psychiatric origin, the physician also may use low-dose antidepressants (venlafaxine, amitriptyline, and doxepin) and also pregabalin ³¹.

In 2009, Cutrer et al. ¹⁵ have investigated the efficacy of botulinum toxin treatment in cephalalgia alopecia patients and obtained improved pain control and hair regrowth following botulinum toxin A injections. They also observed that botulinum increases substance P and calcitonin gene-related peptide-containing cutaneous nerves in the scalp. Botulinum toxin A injections does not block low-level trophic release of neuropeptides such as calcitonin gene-related peptide and allows resumption of substance P and calcitonin gene-related peptide baseline regulation of the hair follicle and hair regrowth ³². However, it should be kept in mind that botulinum toxin A treatment is temporary. The process of painful inflammatory activation, hair follicle regression, and hair loss is repeated after a few months.

Sensory tests revealed that trichodynia patients were significantly more sensitive to touch and to pressure pain and exhibited cranial mechanical hyperesthesia and cranial hyperalgesia ³³. So, gentle scalp maintenance may provide some relief. To support the treatment, it is important to inform the patients about not to use over hot water and harsh shampoos or wear tight pony tail. Other relaxation techniques such as gentle scalp massage may also help in reducing symptoms.

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