Cutaneous sensory disorders
Animals with cutaneous sensory disorders experience neurosensory disturbances in the absence of any detectable dermatologic,
neurologic, or medical condition. The pathology and clinical signs may be generalized or limited to specific body parts. Because
animals cannot verbally report the sensations they experience, consider cutaneous sensory disorder if you observe one of the
following responses to specific sensory stimuli:
1. Allodynia—a pain response to non-noxious stimuli
2. Hyperalgesia—an exaggerated response to typically painful stimuli
3. Marked dysesthesia—excessive response to or avoidance of unpleasant stimuli
4. Pronounced self-directed behavior suggesting that the animal may be responding to a sensory stimulus (e.g. by avoidance, withdrawal, arousal to a discrete or focal stimulus).
While attention-seeking behaviors are typically thought of as owner-directed behaviors (e.g. pawing, jumping, nudging, barking), animals can learn to perform self-directed behaviors (e.g. scratching, licking, chewing, sucking) to receive attention. In response to such behaviors, clients often attempt to interrupt
the behavior by using physical or verbal correction, comforting the animal, or attending to any lesions present; thus, they
reinforce the behavior. Self-directed behaviors occurring only in the presence of selected individuals are strongly suggestive
of attention-seeking behavior. In these cases, observing or videotaping the animal in the presence and absence of such individuals
will help verify the diagnosis.
In people, psychotic conditions can be associated with self-directed behaviors as a result of hallucinations, delusions, or
motor disturbances. Because animals cannot directly report delusional and hallucinatory behaviors, a diagnosis of a psychotic
condition in animals is difficult to confirm and must be presumed. Most conditions involving repetitive motor disturbances
with possible delusional or hallucinatory components (e.g. fly chasing, shadow chasing) are more commonly classified as compulsive disorders; however, it is still important to consider
potential hallucinatory or delusional etiologies when evaluating animals for self-directed behaviors.
Common examples of self-directed behavior include psychogenic alopecia (dogs and cats), acral lick dermatitis (dogs), and
hyperesthesia syndrome (cats). These disorders are syndromes with nonspecific causes rather than specific diagnoses. Thus,
one dog with acral lick dermatitis may excessively lick as an attention-seeking behavior while another licks as a manifestation
of a compulsive disorder. Similarly, one cat presenting for psychogenic alopecia may excessively groom as a displacement activity
while another may groom as a redirected behavior. Because many causes result in similar clinical signs, it is essential that
a specific diagnosis for the behavior be determined for the most effective management.
Psychogenic alopecia is characterized by excessive self-grooming that is initiated or intensified by nonorganic causes or
that persists beyond resolution of an organic cause. Although this syndrome is more prevalent in cats, some dogs do present
with psychogenic alopecia (Virga V, Veterinary Healing Arts Inc., East Greenwich, R.I.: Unpublished data, 2005). Clients may
not see the behavior because the animals, especially cats, may groom reclusively. The predominant clinical signs of this syndrome
in cats are barbering and alopecia, particularly of the medial forelimbs, caudal abdomen, inguinal region, tail, and dorsal
lumbar areas. Physical examination of the alopecic lesions should reveal short, broken hairs that do not epilate easily. Broken
shafts should be evident on microscopic examination of these hairs. Large amounts of hair in the feces are evidence of excessive
self-grooming. Other clinical signs include abrasions or erosions secondary to self-mutilation, secondary bacterial infection,
lichenification, hyperpigmentation, and dermatitic lesions (bright-red, elongated, oval streaks or plaques).7
Because psychogenic alopecia has been noted in captive wild cats and is reported to be more prevalent in strictly indoor cats,
displacement grooming in response to social or environmental stressors should be considered (Virga V, Veterinary Healing Arts
Inc., East Greenwich, R.I.: Unpublished data, 2005).8,9 Other potential causes include anxiety, stereotypic behavior, compulsive disorders, and redirected behaviors.
Acral lick dermatitis
Acral lick dermatitis is characterized by firm, raised, ulcerative plaques that develop because of chronic licking. Single,
unilateral lesions of the cranial carpus and metacarpus are most prevalent; additional lesion sites include the cranial radius,
metatarsus, and tibia.7 Secondary bacterial infection is common and may contribute to these lesions being intensely pruritic. As such, a sustained
course of antimicrobials is often advisable.
Acral lick dermatitis may be organic or psychogenic in origin. Psychogenic associations include displacement activities in
response to social or environmental stress, anxiety, stereotypic behaviors, compulsive disorders, and redirected behaviors.
Some evidence of familial inheritance and breed predisposition exists, with Labrador retrievers, Great Danes, Doberman pinschers,
German shepherds, and some northern breeds being over-represented.9,10