What is cutaneous dysaesthesia?
Cutaneous dysaesthesia is a condition defined as an unpleasant and abnormal sensation in the skin. In the mouth, a similar sensation is called oral dysaesthesia.
It can be classified as generalised or localised. There are multiple variants of localised cutaneous dysaesthesia, which differ in location, duration, and symptom severity.
Who gets cutaneous dysaesthesia?
Anyone can get cutaneous dysaesthesia. There is a possible female predominance in some variants, such as scalp dysaesthesia and notalgia paraesthetica .
What causes cutaneous dysaesthesia?
Generalised cutaneous dysaesthesia is associated with neurological diseases, including:
- Autoimmune disorders, such as acute inflammatory demyelinating polyneuropathy and multiple sclerosis
- Peripheral neuropathies, which may be hereditary, metabolic, or induced by infection or toxin
- Thalamic infarcts
- Alcohol or drug withdrawal
- Endocrine diseases, most commonly diabetes.
Localised dysaesthesia often follows nerve trauma, impingement, or irritation. This can be intracranial (in trigeminal trophic syndrome), spinal, or peripheral.
- Trauma might be iatrogenic (including surgery) or spontaneous (due osteoarthritis, hyperostosis, a fracture, tumour, arterial ischaemia, or tight clothing) .
- Infections can also cause nerve injury including herpes zoster, herpes simplex, and leprosy .
- Dysaesthesia associated with syringomyelia may be due to impairment of supra-spinal pathways, disinhibition of sympathetic neurons, and aberrant spreading of nociceptive afferent nerves (the fibres that send information to the brain) .
Other reported causative associations with cutaneous dysaesthesia are described below.
- Notalgia paraesthetica has been linked with multiple endocrine neoplasia type 2A (MEN2A) caused by RET gene mutations .
- Brachioradial pruritus can be exacerbated by sun exposure .
- Meralgia paraesthetica has been associated with type 2 diabetes and obesity .
- Substance P, a neuropeptide, is postulated to play a key role in trichodynia by promoting mast cell degranulation and neurogenic inflammation in the hair follicle .
- Psychological stress and generalised anxiety disorder can aggravate symptoms or result in somatisation . See Psychosocial factors in dermatology.
What are the clinical features of cutaneous dysaesthesia?
Dysaesthesia or paraesthesia describes positive cutaneous symptoms such as pruritus, burning, crawling, stinging, hyperaesthesia, allodynia, and pain; and negative symptoms such as anaesthesia or cold sensation. One or more of these symptoms may be present.
The examination of the affected area may be normal or there may be signs of the underlying disease if any, or secondary to rubbing and scratching (if itchy).
Generalised cutaneous dysaesthesia
Generalised cutaneous dysaesthesia presents with dysaesthesia affecting most or all of the skin surface. Symptoms can be exacerbated by temperature change, heat, or the touch of clothing.
Localised cutaneous dysaesthesia
Localised cutaneous dysaesthesia presents with symptoms confined to one area.
- Symptoms can be unilateral or bilateral.
- The skin may appear normal.
- Secondary dermatological changes associated with pruritus may include excoriations, bruising, hyperpigmentation, and lichenification.
- If nerve impingement involves sympathetic pathways as well as sensory nerves, localised dysaesthesia may be accompanied by hyperhidrosis .
Signs of cutaneous dysaesthesia
How is localised cutaneous dysaesthesia classified?
Localised cutaneous dysaesthesia has been classified in the following conditions.
- Brachioradial pruritus affects the skin overlying the brachioradialis muscle of the forearm, that is, on the dorsolateral aspect of the arm around the elbow .
- Glossodynia or burning mouth syndrome is confined to the oral mucocutaneous membrane and is a form of oral dysaesthesia .
- Genital dysaesthesia may affect the vulva (dysaesthetic vulvodynia) or scrotum (male genital dysaesthesia and scrotodynia) . Perineal dysaesthesia may be accompanied by erythema. See also Pudendal nerve entrapment syndrome.
- Meralgia paraesthetica affects the anterolateral thigh, the distribution of the lateral femoral cutaneous nerve.
- Notalgia paraesthetica affects the skin between the scapula and vertebrae (T2–T6). Forward flexion or extension of the arms may worsen symptoms .
- Scalp dysaesthesia affects the skin overlying the occipitofrontalis muscle and scalp aponeurosis (C5–C6) . This is sometimes referred to as trichodynia (literally, painful hair) when associated with hair loss or an inflammatory condition of the scalp.
- Hand-foot syndrome is a form of cutaneous dysaesthesia affecting hands and feet during chemotherapy
- The trigeminal trophic syndrome usually affects the ala of the nose (V2 branch of the trigeminal nerve) with subsequent rubbing and picking causing ulceration. The trigeminal trophic syndrome can also involve the buccal mucosa, the tongue, or eye. The tip of the nose (innervated by a branch of V1) is often spared .
What are the complications of cutaneous dysaesthesia?
The main complication of cutaneous dysaesthesia is decreased quality of life and impact on mood and mental health.
How is cutaneous dysaesthesia diagnosed?
Generalised cutaneous dysaesthesia
Generalised cutaneous dysaesthesia is a clinical diagnosis after a detailed history and examination have excluded a primary dermatological disease.
Serological tests may include testing for the following:
- Glycosylated haemoglobin (HBA1c)
- Complement (C3, C4)
- Antinuclear antibody (ANA)
- Antineutrophil cytoplasmic antibodies (ANCA)
- Antibodies to Borrelia burgdorferi (found in Lyme disease)
- Human immunodeficiency virus (HIV) and viral hepatitis
- C-reactive protein (CRP)
- Iron studies
- Vitamin B12
- Vitamin E
- Heavy metal levels
- Angiotensin-converting enzyme (ACE).
Other tests may include:
- Nerve conduction studies to look for demyelinating or axonal neuropathy
- Cerebrospinal fluid (CSF) analysis for oligoclonal bands if demyelination is suspected
- Magnetic resonance imaging (MRI) of the brain and cervical spine if demyelination or ischaemia is suspected.
Localised cutaneous dysaesthesia
The diagnosis of localised cutaneous dysaesthesia is based on clinical suspicion. A comprehensive history and examination are needed to identify any underlying cause. For instance, hyperreflexia, weakness, or autonomic dysfunction can indicate a spinal cord pathology.
Other diagnostic tests may include:
- Serology: antinuclear antibody (ANA), antineutrophil cytoplasmic antibodies (ANCA), C-reactive protein (CRP)
- Skin biopsy
- Imaging: plain X-rays, or MRI of the cervical/thoracic spine for osteophytes, cervical ribs, disc herniation, spinal lesions, or fractures.
What is the differential diagnosis for cutaneous dysaesthesia?
The differential diagnosis of cutaneous dysaesthesia should be broadened if the skin is normal or abnormal (eg, lichenification might be due to eczema, nasal ulceration might be due to skin cancer).
Somatisation is sometimes implicated with cutaneous sensory disorders such as compulsive skin picking.
What is the treatment for cutaneous dysaesthesia?
Cutaneous dysaesthesia is difficult to treat effectively. Management depends on the cause, body site, and severity of symptoms.
Symptomatic therapy may include:
- Capsaicin cream
- Local anaesthetic patches
- Low-dose tricyclic  or another antidepressant 
- Antiepileptics including gabapentin, pregabalin, and carbamazepine 
- Topical amitriptyline 1% with ketamine 0.5% for brachioradial pruritus 
- Antipsychotic medications such as venlafaxine and pimozide
Additional treatments may include:
- Propranolol  and possibly cannabinoids  (reported as useful for trichodynia)
- Physical barriers to reduce manipulation and ulceration of tissue in trigeminal trophic syndrome, such as gloves, nocturnal thermoplastic facemask, and night-time arm splinting
- Transcutaneous electrical muscle stimulation, narrow-band ultraviolet radiation, and botulinum-A injections for notalgia paraesthetica 
- Intralesional steroid injections for meralgia paraesthetica.
What is the outcome for cutaneous dysaesthesia?
Prognosis depends on aetiology, symptom severity, and treatment response. There is no effect on life expectancy.