Etiology

• Speculated that the cause is multifactorial, or that the syndrome is not a distinct entity with a single cause but rather can develop from a variety of different factors.
• Genetic liability.
• Social and environmental stressors (eg new additions to household, alterations in schedules, moving house).
• Anxiety-related conditions are notoriously heterogeneous and vary depending on duration of condition (which likely alters neurochemical pathology) and brain regions recruited. Progress is being made in the rodent and human literatures through investigations into effects of sensory stimulation.
• Processing and extent of sensory stimulation and/or its perception is key.
  • Arousal is associated with a cutaneous response generated by types 1 and 2 slow-adapting (SA) epidermal units.
  • Rate of discharge that is proportional to the amount of displacement of the hair or the indentation of the skin in cats.
  • Interactions of SA units with rapid-adapting (RA) units in the vibrissae around the face, lips, mouth, and guard hairs to generate the classic biting response that follows vibrissae stimulation in predatory situations.
  • Feline body and head posture affect mediation of responses through descending spinal tracts and may augment the duration and intensity of extensor activity.
  • Cutaneous and proprioceptive feedback interacts to program the relative timing of flexor and extensor activity. In the fulminant form these bouts resemble the classic chewing/aggression mediated by the ventromedial hypothalamus/amygdala.
  • Cholecystokinin B (CCK-B) (central brain) receptors are involved in the firing of feline jaw musculature and so may affect the form of some of these behaviors that involve licking or biting.
  • Anxiety, pain and pruritus are related at both the central level and at the level of the dorsal horn of the spinal ganglion  .

Predisposing factors

General

• Injury.
• Pruritic conditions.
• Atopic conditions.
• Non-specific anxiety.
• External reinforcement from owner.
• Anxiety, which can be external or internal, is broadly defined as the apprehensive anticipation of future danger accompanied by somatic symptoms of tension (vigilance and scanning, autonomic hyperactivity, increased motor activity and tension).
  • For anxiety to be pathological it must be exhibited out-of-context, or in a degree or form that would be sufficient to accomplish an ostensible goal.

Specific

• Pruritus/atopy Skin: atopic dermatitis including that due to food allergies Food hypersensitivity and flea bite dermatitis Flea bite hypersensitivity.
• Trauma to tail Tail pull injury, spine or dorsum.

Pathophysiology

• Etiology is complex but doubtless involves numerous serotonin receptors.
  • There is now considerable evidence that nociception and anxiety affect the same serotonin receptors, especially the 5-HT1A and 5-HT2A, which is particularly important for peripheral nociception (Lanfumey et al, 2008).
  • Itch and pain also share peripheral and central pathways (Schmetz, 2010; Patel and Dong, 2010).
  • Sensitization of a stimulus response to pain or itch is possible at both the peripheral and central level and may involve endorphins, cytokines, histamine, nerve growth factor and other receptors/neurotransmitters already discussed.
• There is virtually no research on feline hyperesthesia so the extent to which social and environmental change and associated anxiety v. endogenous factors contribute to anxiety is unknown.
• In its full-blown form, feline hyperesthesia meets the diagnostic criteria for obsessive-compulsive disorder/compulsive disorder (OCD/CD) (repetitive, stereotypic motor, locomotory, grooming, ingestive, or hallucinogenic behaviors that occur out-of-context to their normal occurrence, or in a frequency or duration that is in excess of that required to accomplish the ostensible goal).
  • When this occurs clients report that their cat is extremely focused in his response to the rippling and that it can be impossible to distract him from it. The behavior may cease only when the cat is exhausted, when physically prevented from responding (eg wrapped in a blanket) or disrupted by a profound (and often startling) sensory change (eg being scooped up and put unceremoniously outside).
• Cats have an atypical response to arousal, in general, when their hypothalamus is stimulated.
  • Cats isolated from other cats for most of the first year of life exhibit a response characterized by galvanic skin responses and disruption of regular sleep rhythms.
  • Excitation of the ventromedial hypothalamus (VMH) and amygdala leads to a defensive response in cats.
  • Stimulation of the lateral amygdala facilitates predatory attack and defensiveness in cats, but stimulation of the lateral amygdala using high intensity also recruits the ventral hippocampus in these behaviors, providing a partial explanation for why repetition is so problematic. The hippocampus plays a major role in associational learning.

Timecourse

• Episodes are several seconds to several minutes in length.
• Early on in the development of the condition the cat can be interrupted from the behavioral responses. As the condition progresses, interruption may not be possible and attempts to do so may be met with frank aggression.