Feline Hyperesthesia Syndrome: Diagnosis and Treatment

Feline hyperesthesia syndrome (FHS) is a challenging condition to diagnose and treat, as its clinical signs can be dramatic and its underlying cause often unclear. According to Dr. Alison Gerken, a clinical veterinary behaviorist, FHS is characterized by episodic rippling or twitching of the skin, agitation, and self-directed grooming or biting.

## Presentation and Diagnosis The presentation of FHS can vary, but common signs include episodic rippling or twitching of the skin, agitation, sudden grooming or biting of the back, tail, pelvic limbs, or flanks, tail chasing or swishing, vocalization, running or hiding, or sudden startle behavior. Episodes are often brief, and many cats appear normal between events. A diagnosis of FHS should be made after ruling out other possible causes, such as inflammatory skin disorders, neuropathic, spinal, musculoskeletal, gastrointestinal, tail, and anal sac pain, and seizures.

## Diagnostic Workup The diagnostic workup for FHS should begin with a careful history and full physical, dermatologic, orthopedic, and neurologic examinations. Useful questions include patient age at onset, episode frequency and duration, whether episodes are stereotyped, whether the patient appears normal between events, and whether identifiable triggers are present. Client video of an episode can also be helpful. The workup may include thorough ectoparasite control, skin cytology, fungal testing, trichography, and anal sac evaluation, as well as advanced imaging, cerebrospinal fluid analysis, or electrodiagnostic evaluation if necessary.

## Treatment Options Therapeutic trials for FHS should address the leading differentials, and may include NSAIDs, prednisolone, oclacitinib, and/or an elimination diet, or levetiracetam if focal seizure activity is suspected. Longer-term medication choices depend on the cat's clinical phenotype, and combination therapy may be necessary. Medications such as gabapentin, pregabalin, venlafaxine, and fluoxetine may be used to manage FHS, depending on the cat's specific needs. The following table summarizes some of the treatment options for FHS: | Medication | Indication | Mechanism of Action | | --- | --- | --- | | Gabapentin | Neuropathic pain, sensory dysregulation | Binds to α2δ subunit of voltage-gated calcium channels, reducing excitatory neurotransmitter release | | Pregabalin | Neuropathic pain, sensory dysregulation | Binds to α2δ subunit of voltage-gated calcium channels, reducing excitatory neurotransmitter release | | Venlafaxine | Arousal, anxiety, pain | Serotonin-norepinephrine reuptake inhibitor, addressing both arousal and pain modulation | | Fluoxetine | Anxiety-related or compulsive phenotype | Selective serotonin reuptake inhibitor, although less effective than SNRIs for neuropathic pain |