neuropathic

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Dermatologic Therapy, Vol. 21, 2008, 32–41 Printed in the United States · All rights reserved

Copyright © Blackwell Publishing, Inc., 2008

DERMATOLOGIC THERAPY

ISSN 1396-0296

Blackwell Publishing Inc

Neuropathic and psychogenic itch

G

IL

Y

OSIPOVITCH

*

,

† & L

ENA

S. S

AMUEL

*

*

Department of Dermatology and

†

Neurobiology and Anatomy, Wake Forest University Health Sciences, Winston-Salem, NC

ABSTRACT:

Neuropathic and psychogenic itch are two entities that have not been well studied.Neuropathic itch is related to pathology located at any point along the afferent pathway of thenervous system. It could be related to damage to the peripheral nervous system, such as in postherpeticneuropathy, brachioradial pruritus, notalgia paresthetica, and in central nervous system damage asa result of spinal cord tumors and demyelinization diseases such as multiple sclerosis. It has manyclinical features similar to neuropathic pain. Patients complain of itch, which coincides with burningsensation, aching, and stinging. Psychogenic itch is related to psychologic abnormalities e.g., itch inobsessive compulsive disorders, depression, and delusions of parasitosis. Although no controlledstudies have been conducted for treatment of neuropathic and psychogenic itch, medications thatare part of the treatment armentarium for neuropathic pain, depression, and anxiety seem to beeffective.

KEYWORDS:

hypersensitization, neuropathic pruritus, neuropeptides, psychogenic pruritus

Introduction

Neurophysiological research in the last 10 yearshas enabled more accurate descriptors of neuralpathways involved in itch response. Microneurog-raphy studies in humans demonstrated a smallsubset of specific C-nerve fibers that are histaminesensitive to transmit itch and not pain (1). Thesefibers activate spinal neurons in lamina 1 of thedorsal horn that are histamine sensitive (2). Fur-thermore, these C-nerve fibers have been shownto have spontaneous activity in patients withchronic itch (2,3). Recent neurophysiology studiesin both humans and primates suggest that thereare other C-nerve fibers that transmit itch that arehistamine insensitive and responds to cowhage, aplant that induces itch and mechanical stimuli.These new fibers are found both in the peripheralnervous system as well as in ascending sensoryneurons in the spinal cord and thalamus (4,5).These nerve fibers also respond to painful stimuli.Therefore, it is quite clear that any damage alongthe afferent pathway can elicit chronic itch.

Psychogenic pruritus involves brain abnormalitiesthat are as yet not well defined. Chronic itch involvesmultidimensional phenomena including emotionaland cognitive factors. Therefore, it is not surprisingthat psychiatric disorders play a role in the etiologyof chronic itch. In the last 5 years there is growingawareness regarding these types of itch, althoughthese types of itch are significantly less studied incomparison to other types of itch.

Definition of neuropathic itch

Neuropathic itch has been defined as an itch initi-ated or caused by a primary lesion or dysfunction atany point along the afferent pathway of the nervoussystem (6). It could be acute but in most cases ischronic and persistent. In many cases neuropathicitch is accompanied by sensory damage experi-enced as parasthesia, hyperesthesia, or hypothesia.It may also occur during recovery from isolatednerve injury such as after burns. Patients can havein the same site both pain sensation and itch.

In many cases it involves peripheral and centralsensitization of nerve fibers. This sensitizationinduces alloknesis, which is an itchy phenomenonthat results from an innocuous stimulus that does notnormally provoke itch. This is similar to allodynia,a common phenomenon in patients with neuropathicpain where a light touch can induce pain. Of note,

Address correspondence and reprint requests to: Gil Yosipovitch, MD, Wake Forest Medical Center, Department of Dermatology, Medical Center Blvd., Winston Salem, NC 27157-0001, or email: [email protected].


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this phenomenon is not unique to neuropathicitch and has been reported in inflammatory itchsuch as atopic eczema (3). Alloknesis and allodyniacan coincide in several forms of peripheral neuro-pathies (6). Characteristics of neuropathic itchthat differentiate it from other forms of itchinclude the following:1. Itch is associated with other sensory symptoms

in a dermatomal distribution.2. The presence of other neurological sensory

signs or neural damage including motor damage,or autonomic damage.The presence of neuropathic itch does not

exclude the concurrent presence of other typesand mechanisms of itch, e.g., patients with chronickidney disease itch and human immunodeficiencysyndrome may have neuropathy as well as othersystemic causes for their itch.

Pathophysiology

Mechanisms of neuropathic itch are incompletelyunderstood. Some of the proposed mechanismsinclude itch associated with local nerve damage;central neuronal deprivation of afferent input;and central hypersensitivity of nerve fibers. Thefirst mechanism suggests that itch fibers, whichhave large innervation territories extending beyonddermatomes, present when local damage occursto C nerve fibers that transmit both pain and itch.The second hypothetical mechanism suggests thatcentral itch neurons fire excessively when they aredeprived of their afferent input. Another possiblemechanism is lack of inhibitory neurons for itchin the spinal tract. Chronic neuropathic itch canalso result from long-term changes in corticalsomatosensory pathways. This can explain theoccurrence of alloknesis and allodynia in neuro-pathic itch which are related phenomena of centralsensitization (3)

Clinical signs of neuropathic itch

Neuropathic itch can coincide with pain as seenin postherpetic neuralgia and notalgia paresthetica.Characteristic sensory complaints associated withneuropathic itch are burning, parasthesia, tingling,and stinging. Localized itching can follow der-matomes such as the dorsolateral aspect of thearms in brachioradial pruritus and unilateral itchmidback in dermatomes at the level of T2-T6 innotalgia parasthetica.

Patients with neuropathic itch can complain ofsensory deficits for touch and temperature such

as in postherpetic neuralgia. Also, patients oftenreport unilateral itch after a stroke. Perinasal itchor persistent unilateral scalp itch may be associ-ated with brain tumors (6).

Evaluation of a patient with neuropathic itch

Patients with neuropathic itch may present withvarying symptoms. Therefore, a thorough historyand physical examination are paramount in dis-tinguishing symptoms and approaching the correcttherapeutic options. Patients with neuropathic itch(with or without accompanying pain) have sensorylosses in the affected areas. Close attention tofeatures exhibited on presentation such as paras-thesia, hypoesthesia, and hyperalgesia can guide theclinician in diagnosing neuropathic itch. A thoroughneurologic exam performed by a neurologistmay help uncover associated sensory abnormalities,e.g., light touch, pinprick, temperature strength,perception, and vibratory sense. In patients withfacial and scalp itch a full neurologic exam of cranialnerve functions is required. This can be followedby skin biopsy to assess nerve fibers density withPGP9.5 (Protein Gene Product 17.5) marker couldbe helpful in establishing the diagnosis (7). Quanti-tative sensory testing to assess the function ofC-nerve fibers can provide important informationabout the function of the C-nerve fibers is affectedareas. Electromyography and nerve conductionstudies in cases suspected of impingements ofnerve roots. Magnetic resonance imaging of thespine is recommended to locate suspected nerveimpingement such as in brachioradial pruritusand notalgia parasthetica. Brain magnetic resonanceimaging should be performed in cases with nasalitch to rule out brain tumors in the ventriclesas well as cases of trigeminal trophic syndrome(TTS) where a meningioma could cause this itch.Neuropathic itch can occur with secondary skinfindings such as prurigo, lichenification, as wellas excoriations; however, the itch could also bewithout any skin signs. A normal neurophysicalexamination does not necessarily rule out neuro-logic disease.

Peripheral neuropathic itch

Postherpetic neuralgia (PHN).

PHN is consideredthe prototype of painful neuropathy. Oaklanderwas the first to perform a study on postherpeticitch (PHI) and found that among 153 patientswith prior shingles, 48% reported itching (8). A

Yosipovitch & Samuel

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larger study analyzing data of 600 patients fromthree independent centers demonstrated that PHIis a common symptom among patients with PHN(9). Itch severity can range from mild to severe.Severe PHI is more frequent on the face and head(8). The patients can experience the itch and painsimultaneously in the same dermatomal distribu-tion affected by PHN. Common descriptors inaddition to itch were burning and stinging sensa-tion. The present authors previously documenteda significant loss of epidermal nerve fibers inpatients with PHN, some of which had itch, whichcorrelated to their loss of sensation to warmthand heat pain (10). Treatments for PHI are similarto those of PHN pain including neurotropic drugssuch as gabapentin or pregabalin (11–15), as wellas topical anesthetics, e.g., Eucteic mixture of localanesthetics (EMLA) cream and lidocaine patch aswell as applications with capsaicin (16).

Brachioradial pruritus

Brachioradial pruritus (BP) is a localized neuropathicpruritus of the dorsolateral aspect of the arm (17–19).It can also involve the shoulders and neck (17). Itis aggravated in many cases during sun exposureand is more frequent during the summer while itremits during winter. It is more common in thosewho are active in outdoor sports such as tennisplayers and cyclists. It has been suggested that inmany cases it is a result of compression to the cer-vical nerve root in the level of C5-C8 (19,20). RarelyBP can also be associated with spinal tumors, espe-cially in those patients who present with multiplesensory and motor deficits (17,21). There are caseswere there is no evidence for spinal nerve damage,and patients have classical clinical presentationassociated only to sun exposure. Wallengren foundBP to be associated with a reduction in epidermalnerve fibers in the epidermis and papillary dermis(18) very similar to changes that occur after pho-totherapy. Therefore it was suggested that neuro-logical damage to nerve fibers in this disorder mayarise from either the cutaneous nerves or from themore proximal sensory pathways (22). A commonclinical symptom in patients with BP is the “icepack sign,” patients reporting that application ofice pack on the affected areas temporarily reducestheir itch.

Brachioradial pruritus is often refractory totreatment; however, successful treatments wereachieved with topical capsaicin, oral gabapentin(23,24) and pregablin, carbamazepine, lamotrigine,and surgical approaches for tumors or when thereare significant sensory and motor deficits (17).

Notalgia parasthetica

Notalgia paresthetica (NP) is a sensory nerveentrapment syndrome involving the posteriorrami of T2-T6 nerve root associated mainlywith degenerative changes in the vertebra (25).Patients typically present with unilateral itchingof the mid and upper back in the distributionof T2-T6 dermatomes. The itch is occasionallyaccompanied by burning pain, paresthesia,and/or hyperesthesia, which results in a well-circumscribed hyperpigmented patch in thesymptomatic area (26,27) similar clinically tomacular amyloidosis.

Notalgia paresthetica can be successfully treatedwith capsaicin (28), gabapentin, EMLA cream, andparavertebral local anesthetic blocks, cervicalepidural steroid injection, phenytoin. Other therapiesinclude physiotherapy, neck traction, and cervicalmanipulation.

Cheiralgia parasthetica

Cheiralgia parasthetica is an itch that is confinedto the radial aspect of the lower arm caused byentrapment of the radial nerve (18).

Trigeminal trophic syndrome

Trigeminal trophic syndrome (TTS) is an uncommoncause of localized itch and pain resulting fromdamage to the trigeminal nerve. It can be associatedwith numbness, burning and crawling sensations.Physical signs include excoriations and facialulcerations. The nasal ala is almost universallyinvolved, but the cheek, temple, and frontal scalpcan also be affected. TTS most commonly occurs(75% of cases) after surgical ablation of the Gasse-rian ganglion. Many cases are initially misdiag-nosed as dermatitis artefacta or psychogenicpruritus. The treatment for TTS includes neuro-leptics such as carbamazepine, gabapentin, andpregabalin (29).

Keloid and burn scars

Keloids can cause neuropathic itch mainly alongthe border of a keloid lesion, whereas less fre-quently, pain involves the center of the keloid.Mechanistically, collagen deposition may inducean entrapment neuropathy affecting pain fibersin the center of the keloid and unmyelinated Cnerve fibers that transmit itch at the periphery(30). Pruritus is a common manifestation duringrecovery from burns (31).


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Pruritus in postmastectomy scars is suggestedto be a phantom itch similar to phantom pain (6).

Other forms of neuropathic localized itch havebeen reported such as anogenital pruritus is asymptom of lumbosacral radiculopathy (32).

Central neuropathic itch

Itch from central nervous system lesions is far lesscommon than from peripheral nerve lesions.Several underlying brain pathologies includetumors, strokes (33), abscesses (34), and Creutzfeldt-Jakob disease (35).

Spinal tumors and neuropathic itch

. Cavernoushemangiomas (cavernomas) of the spinal cord arerare congenital malformations that comprise 5%of all intramedullary lesions. The rostral dorsallocation of the cavernoma increases its likelihoodof causing both pain and itch (36). Other tumorssuch as ependymoma have been associated withneuropathic itch (2). Peripheral acting lidocainereduced the central itch in cavernomas (36). 5%lidocaine patch, EMLA cream, or gabapentin pro-vide moderate itch relief.

Multiple sclerosis

Pruritus has been reported in 5% of patients withmultiple sclerosis (MS) (6). It presents with aparoxysmal pattern of itch. The paroxysmal

itching often awakens the patient from sleeping,and may be spontaneous or triggered by movementsimilar to the Lhermitte sign, causing pain. Theseparoxysmal symptoms are considered to be theinitial presentation of MS (37). The symmetrical,segmental, and paroxysmal nature of these MSphenomena supports their neurological origin.The pruritus and dysesthesias of MS are amendableto therapy with carbamazepine.

Phantom itch has been reported followingmastectomies, as mentioned previously, this in factcould be related to peripheral damage from scarsor from brain alterations post nerve damage.

Psychogenic pruritus

Psychogenic pruritus is considered psychiatric inorigin. It is characterized as an excessive impulseto scratch, gouge, or pick at normal skin. Althoughpsychogenic pruritus poses a clinical challenge tothe dermatologist and the psychiatrist, it has notbeen labeled a distinct diagnostic entity in the

Diagnostic and Statistical Manual of MentalDisorders

, Fourth Edition (DSM-IV). Generally,psychogenic pruritus is a diagnosis of exclusion andcan be made after ruling out other causes of pruritusthat may mimic this condition. Its incidence inthe general population is unknown; however, itsincidence is 2% in patients seen in dermatologyclinics (38). There is a female predominance withaverage age of onset between 30 and 45 years of age.

Table 1. Treatment for neuropathic and psychogenic itch

Condition Therapy

Central neuropathic itchMultiple sclerosis Carbamazepine, gabapentinSpinal tumors Lidocaine patch, EMLA cream, gabapentinPhantom itch Regional and intrathecal nerve blocksPeripheral neuropathic itchPost herpetic neuralgia Gabapentin, pregablin, carbamazepine, IV anesthetics,

topical capsaicinBrachioradial pruritus Gabapentin, pregablin, carbamazepine, topical

capsaicin topical 1% mentholNotalgia paresthetica Gabapentin, botulism toxin A, EMLA cream, paravertebral nerve blocks,

phenytoin, cervical epidural steroid injection, topical capsaicinTrigeminal trophic syndrome Carbamazepine, gabapentin, pregablinPsychogenic itchDepression SSNRIs, SSRIs, TCAs, doxepin, psychotherapyObsessive compulsive disorders SSNRIs, SSRIs, TCAs, behavioral therapyDelusions of parasitosis Antipsychotics, e.g., pimozide, risperidone, olanzapine, quetiapine

Common treatment modalities used in dermatology, psychiatry, and neurology for neuropathic and psychogenic itch conditions.

SSRIs, selective serotonin reuptake inhibitors; SSNRIs, selective serotonin and norepinephrine reuptake inhibitors; TCAs, tricyclic antidepressants.


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Psychogenic pruritus can occur along with aknown psychologic abnormality, or concurrentlyin a patient suffering from another type of itch.Psychiatric disturbances are common in patientswho suffer from chronic itch (39). In a large popu-lation study in Oslo there was a significant corre-lation between mental stress and itch as well aspain (40–42). Depression, obsessive compulsivedisorder, anxiety, somatoform disorders, mania,psychosis, and substance abuse have been associ-ated with itch (43). Some studies suggest depressionmay be the primary clinical state in psychogenicpruritus (44). Several psychiatric comorbiditiessuch as body dysmorphic disorder, trichotilloma-nia, kleptomania, and borderline personality werereported in these patients (38). The secondary skinchanges associated with psychogenic pruritus arecommonly found on body areas that are mostaccessible to the hand such as extensor surfacesof the arms and legs, abdomen, thighs, and upperparts of the back and shoulders (38,44), with theface being the most common site (45). The sec-ondary skin signs can be seen in varying stages ofevolution from discrete superficial excoriations,erosions, or even ulcers to thickened hyperpig-mented nodules to hypopigmented atrophic scars(46). These may vary in number from a few to severalhundred and vary in size from a few millimeters toseveral centimeters. Often, patients report picking,rubbing, scratching, or inserting objects to relievethe pruritus. Therefore, the lesions may be painful,bleed, itch, ulcerate with features of delayed healingas a result of recurrent picking similar to chronicitch sufferers of other types. However, the itchcould also be without any skin signs. Although thepatients may be fully aware of what they are doingthey are often powerless to stop.

Patients with itch suffer from low self imageand have difficulties coping with aggression (47).A recent study in 111 hospitalized psychiatricpatients in an open ward who suffer from schizo-phrenia and affective disorders, found that 32% ofthose screened reported suffering from itch afterother causes of itch were ruled out (48). These resultsuggest that psychogenic itch may be a commonsymptom among psychiatric patients.

Obsessive compulsive disorder is a commoncomorbid condition in psychogenic pruritus (49).Obsessive-compulsive symptoms are chronic andpatients can present with behaviors that are pre-ceded by increased tension and anxiety followedby gratification or relief when excoriating the skin(47). Pruritus associated with obsessive-compulsivespectrum disorder is characterized as that ofrecurrent, intrusive thoughts that lead to compulsive

skin picking, hair pulling, and excoriations (39).Mast cell degranulation and cytokine release is seenwith the itch-scratch cycle. Therefore, recurrentitching can lead to an itch-scratch cycle releasingpruritogenic factors further contributing to theobsessive-compulsive interplay.

Delusions of parasitosis

Although delusions of parasitosis are a purely psy-chiatric problem, patients typically present to adermatologist with primarily dermatologic com-plaints. They typically resist referral to psychiatristsand often seek help from several medical profes-sionals for evaluation of symptoms that havespanned over a period of several months or years(46,50,51). Therefore it is important to establishtrust in these patients through the doctor–patientrelationship. Initially, a thorough evaluation to prop-erly diagnose delusions of parasitosis is important.

Delusion of parasitosis, or psychogenic parasi-tosis, is a rare psychiatric disorder in which thepatient has a fixed, false belief that he or she isinfested with an insect or parasite. Defined as amonosymptomatic hypochondrial psychosis (MHP),sufferers of delusions of parasitosis have lesionsproduced consciously in response to the demandsof a delusional belief (44).

Patients often describe self-mutilating behaviorby picking or scratching a discrete area of skin inan effort to remove the insect and may also com-plain of insomnia. When evaluating a patient whomay have delusions of parasitosis, it is importantto rule out other thought disorders. Other differ-entials include alcoholism or drug addictions, anddelusions secondary to another mental or physicalillness other than the fixed false belief that one isinfested with parasites. Alcohol withdrawal, cocaine,and amphetamine use can induce formication anda delusional state similar to that of delusions ofparasitosis. Therefore, appropriate physical, labo-ratory and toxicology examination, skin biopsy,and wet preparations of skin scrapings can be per-formed to rule out a substance abuse and/or anorganic cause.

On physical examination, skin findings rangefrom none at all to discrete scars, ulcers and exco-riations, and prurigo nodularis visible on the face,legs, and arms, which may indicate a factitiousorigin: evidence of the patient’s effort to dig outparasites (52). The matchbox sign is a pathogno-monic sign where patients present with specimensof “parasites” they have collected including bitsof skin, lint, dried blood, and tissue paper asevidence (52).


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Evaluation of a patient with psychogenic pruritus

In psychogenic pruritus, an evaluation of whetherthe disease is purely psychiatric, medical, or acombination of both should be determined. Sys-temic, neuropathic, and dermatologic causes ofitch should be ruled out. A good history and thor-ough physical examination followed by laboratoryinvestigation with a complete blood count includ-ing an erythrocyte sedimentation rate, thyroid, liver,and renal function tests should be performed.

A full dermatologic examination should be con-ducted to survey for excoriations, scars, ulcerations,erythema, and any evidence of infection. A detailedhistory of the excoriation episodes should begin withinquiries into the location, onset, timing, method,precipitants, alleviating, and aggravating factors sur-rounding the excoriations, thoughts and emotionsbefore, during, and after the excoriation episode.

A history taking of sleep patterns, history ofdepression, suicidal ideations, or other negativefeelings and self mutilating behaviors should beconducted. It is also important to ascertain previ-ous use of psychiatric medications and their effecton itch. Referral to a psychiatrist or a psychologistis highly recommended after the initial evaluationby the dermatologist. The mental health profes-sionals can assess the patient with psychogenic itchwith a structured psychiatric interview includinga full mental status, and the Beck DepressionInventory for self-reported depression symptoms.Complications of psychogenic pruritus span medicaland psychiatric lines. Patients experience shame orembarrassment surrounding their behavior and oftendo not disclose their habit to doctors or relatives. Asmentioned previously, cases of psychosis or delu-sions of parasitosis who present to dermatologistsare difficult to deal with. It is not recommended toconfront the patient with the diagnosis and it isoften helpful to suggest to him to seek the help ofa mental health expert as an adjunctive measureto reduce his itch intensity and anxiety.

Similar systemic treatments for neuropathic itch and psychogenic itch

Neuropathic itch and psychogenic itch are a ther-apeutic challenge for dermatologists. Treatmentwith standard measures used by dermatologistsfor itch such oral antihistamines and topicalsteroids are of no help. Therapies for treating neu-ropathic itch often include the same medicationsused for psychogenic itch such as neurolepticse.g., gabapentin, pregablin, antidepressants from

the tricyclic medications, amytriptyline as well asselective serotonin and norepinephrine inhibitors,mirtazapine, and duloxetine as well as paroxetine.Often, a combination of therapies is needed to treatthe itch and pain symptoms. There are no con-trolled studies that examine the efficacy of thesemedications for both entities and therefore it iscurrently difficult to accurately assess the efficacyof these treatments. Table 1 summarizes the treat-ment modalities for neuropathic and psychogenicitch.

Neuroleptics

Anticonvulsants such as gabapentin, pregabalincarbamazepine, and lamotrigine have demonstratedefficacy in case reports in treatment of neuro-pathic itch. These drugs appear to have mood-stabilizing properties and anxiolytic benefits (53).

Gabapentin is a structural analog of the neu-rotransmitter gamma-aminobutyric acid and a potentanticonvulsant. It is commonly used for neuro-pathic pain and approved by the FDA for posther-petic neuralgia. Its exact mechanism is unknown,but it has been effective in the treatment ofbrachioradial pruritus (24), and MS (14). It is alsoused for anxiety. The initial dose is 300 mg oncedaily titrated every 3 days by 300 mg up to maxi-mum dose of 2400 mg/day. Pregablin is a new oralmedication that is chemically related to gabapentin.It is used for treating neuropathic pain and seemsto work for neuropathic itch as well (53) as fordepression and anxiety (54). The initial dose is 50–75 mg and can be increased up to 300 mg a day.

Selective neuroepinephrine re-uptake inhibitors

Duloxetine, a selective serotonin and norepineph-rine reuptake inhibitor, is the first antidepressantto be licensed for the treatment of diabeticperipheral neuropathic pain (55,56). The authors’limited experience with this drug for neuropathicitch does not seem to suggest that it is effectivetreatment for neuropathic itch; however, it maybe effective for psychogenic itch associated withdepression and anxiety. Another SNRI mirtazap-ine seems to be effective in patients with chronicneuropathic itch especially those with nocturnalattacks and suspected central sensitization (57).The effective antipruritic dose is 15 mg, higher dosesdo not seem to be of any additional effect andcause more side effects. Paroxetine, a SSRI hasbeen reported to be effective for itch of differenttypes in a small controlled double blind study (55).A recent study from Germany (58) has also shown


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that this antidepressant has anti itch properties indifferent types of itch.

Tricyclics antidepressants

For many years TCIs have been used for depressionas well as for neuropathic pain. Amityriptyline wasreported to be useful in some cases of neuropathicitch. The initial dose is 10 mg three times daily or25 mg once a day at bedtime. Doxepin (Sinequan)is an antidepressant with potent antipruritic, anti-histaminic, and antidepressant properties. It hasbeen used for different types of itch includingpsychogenic (45) and neuropathic itch. It is pre-scribed at doses of ranging from 25 mg up to150 mg at bedtime as a result of its highly sedatingproperties. Typically 6–8 weeks of therapy isneeded before results are seen. Nowadays, the useof tricyclic antidepressants in psychiatry is limitedas a result of the higher efficacy and safety profileof the SSRIs (59).

Combination therapy

A combination of mirtazapine and pregablin orgabapaentin has been reported to be useful tocontrol chronic itch. The present authors havegained experience in using this regimen in severalcases of chronic severe neuropathic itch of PHNitch and brachioradial pruritus.

Specific treatments for neuropathic itch

Botulinium toxin A injection

Recently a pilot study described the successful useof Botulinium toxin A (Botox) for the treatment ofnotalgia paresthetica in two patients (60). The toxinwas injected to several points along the involveddermatome in a dose ranging between 16 and 25units. The rationale for the use of Botox is that itblocks acetylcholine, which is a mediator involvedin itch transmission. This treatment has also beenreported to be successful for PHN neuropathicpain (61,62).

Specific pharmacotherapy for psychogenic itch

Pimozide, a neuroleptic medication, is the treat-ment of choice for delusions of parasitosis given

at doses of 1–10 mg/day. The most common sideeffects are extrapyrimodal symptoms (tremor, rigidity,bradykinesia) and anticholinergic side effects (drymouth, blurry vision, tachycardia, constipation).Extrapyrimidal side effects can be treated withbenztropine 1–2 mg up to four times daily asneeded, or diphenhydramine 25 mg three timesdaily as needed. Reports indicate that pimozidecan cause prolonged QT interval requiring baselineand periodic electrocardiographic monitoring.Recently, olanzapine, a newer atypical antipsychotichas been reported to be an effective therapy fordelusions of parasitosis with initiation dosage of2.5–5 mg/day increased up to 10 mg/day (63).Major side effects of this drug were high levels oftriglycerides and hyperglycemia. Risperdone andother antipsychotics are effective for therapy fordelusions of parasitosis with therapeutic dosagesbeginning at 1 mg once daily as initial startingdosage (64). Common side effects include anxiety,dizziness, and rhinitis (65).

Psychotherapy

Basic psychodynamic intervention and counselingwith a psychotherapist are important to addressmood and personality disorders and family tension.There are few studies on psychotherapy for treatmentof itch and scratching in dermatologic patients.Cognitive behavioral therapy to prevent scratchingmay be of help to patients with obsessive compul-sive disorders as well as depression. Behavioraltherapy based on positive reinforcement of tensionreduction and not scratching (66). For alterationof itching perception, techniques of imaginationtraining of relaxation and perceptions of sensationsinvolved in attenuating itch such as cooling maybe of help in reducing the itch intensity. Theimportance of insight counseling for the cessationof the skin picking, compulsive and impulsivebehaviors should be stressed to the patient (66).

Dermatologic approach to neuropathic and psychogenic itch

The dermatologic approach to the treatment andmanagement of psychogenic pruritus may includeantihistamines, moisturizers, topical steroids,antibiotics, and occlusive dressing. Moisturizingwith lotions and other lubricants can help withthe xerosis that can often exacerbate the pruriticcondition and is also associated with repetitivescratching, damaging the stratum corneum.

Patients can present with inflammation, infec-tions, and ulcers as a result of their itch. Therefore,


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wound care is paramount along with antibioticswhen there is evidence of underlying infection.Occlusive dressing is helpful in preventing furthermanipulation of existing skin lesions by trauma orexcoriations. This approach is particularly helpfulin patients who excessively pick on their skin suchas in prurigo nodularis.

Cooling of the skin with topical 1% mentholmay have some role in itch relief in patients withbrachioradial pruritus, who report that ice packsreduce their itch for hours.

Topical anesthetics such as lidocaine patchesand EMLA cream have been reported to be effectivefor different types of neuropathic itch especiallythe peripheral types. Pramoxine is a less potentanesthetic with anti pruritic effect (67).

Topical capsaicin, the active ingredient in chilipeppers, has been reported to be useful forpostherpetic neuralgia, notalgia paresthetica, andbrachioradial pruritus (23). Topical capsaicinexerts its effects by rendering the skin insensitiveto pain. Topical capsaicin at higher concentrationsof 0.075% and 0.1% seem to be significantly moreeffective than the lower one of 0.025%. Topicalcapsaicin initially causes burning sensations andis not recommended to be used in patients withpsychogenic itch. The addition of topical anes-thetic EMLA cream prior to initiation of topicalcapsaicin has been instituted to further counter-act the sensation and irritation (68) and can alsoincrease the antipruritic affect as both medicationstarget different receptors.

Topical aspirin has been reported to reduce itchof lichen simplex chronicus, a form of localizeditch (69). The authors have found it a useful treat-ment in several forms of peripheral neuropathicitch e.g., PHN and notalgia parasthetica.

Conclusion

Neuropathic and psychogenic itches remain chal-lenging diagnostic and therapeutic conditions.They require in many cases the help of neurologist,pain specialist, and psychiatrists. Future studiesin this field and in particular therapeutic controlledtrials will enable us to provide better treatment tothese tormenting types of itch.

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