What could be causing unbearable interior itching and a sensation of searching for pressure in a 7-month post-fistulotomy patient, especially when sleeping, despite decreased localized pain?

Post-Fistulotomy Neuropathic Pruritus and Phantom Sensation

This patient is experiencing neuropathic pruritus with phantom sensory phenomena—a recognized complication of perianal surgery caused by nerve damage during the fistulotomy procedure. 1

Understanding the Mechanism

The "interior itch" and sensation of "searching for pressure that's no longer there" are classic features of neuropathic pruritus, which arises from pathology affecting peripheral nerves during surgical dissection. 1 This manifests as:

• Burning, paraesthesia, stinging, and tingling accompanying the pruritus 1
• Phantom sensations where the nervous system creates false perceptions of pressure or presence 1
• Worsening at night and during rest, which is characteristic of neuropathic itch 1
• Increased distress during inactivity, particularly when trying to sleep 1

The 7-month timeline is significant—as acute surgical pain resolves, the underlying nerve injury becomes the dominant symptom, explaining why the patient feels "worse" despite less localized pain. 1

Immediate Diagnostic Considerations

Before confirming neuropathic pruritus, rule out perianal dermatitis or fungal infection by examining for:

• Maculopapular rash with satellite borders (fungal) 2
• Erythema in specific patterns (contact dermatitis) 2
• Signs of moisture-related skin breakdown 2

However, the internal/phantom quality of this patient's symptoms strongly suggests neuropathic rather than dermatologic pathology. 1

Treatment Algorithm

First-Line Pharmacotherapy

Start with gabapentin or pregabalin (anticonvulsants effective for neuropathic pain and pruritus):

• These medications target nerve fiber dysfunction and have evidence for neuropathic pruritus 1
• Titrate gradually to minimize side effects 1

Second-Line Options

If anticonvulsants provide insufficient relief:

• Tricyclic antidepressants (doxepin) for both neuropathic symptoms and sleep disturbance 3
• Mirtazapine (tetracyclic antidepressant) which addresses both itch and anxiety 1, 3
• SSRIs (paroxetine, sertraline) if depressive symptoms emerge 1, 3

Adjunctive Measures

• Topical capsaicin may help desensitize peripheral nerve endings, though application to perianal area requires caution 1
• Cognitive-behavioral therapy specifically for itch-related coping, as psychological distress amplifies neuropathic symptoms 1

Addressing the Psychological Component

This patient's fear of permanent symptoms requires direct acknowledgment. 1 The distress itself worsens itch perception through stress-activated neural circuits in the hippocampus. 1

• Neuropathic pruritus often improves over 12-18 months as nerve regeneration occurs 1
• Pharmacotherapy combined with reassurance significantly improves outcomes 1
• Sleep disturbance must be addressed, as it creates a vicious cycle worsening both itch and psychological distress 1

Critical Pitfalls to Avoid

Do not dismiss this as "psychogenic" without treating the neuropathic component first. 1 While psychological factors amplify symptoms, the primary pathology is nerve injury from surgery. 1

Do not assume hemorrhoids or residual fistula disease without examination—the phantom/internal quality distinguishes this from structural pathology. 1

Do not delay treatment—chronic untreated neuropathic pruritus leads to anxiety, depression, and PTSD in up to 27% of patients. 1

Specialist Referral Indications

Refer to colorectal surgery if:

• Examination reveals structural abnormality (abscess, recurrent fistula, stricture) 1
• Symptoms suggest nerve entrapment requiring surgical release 1

Refer to pain management/neurology if:

• First and second-line medications fail after 8-12 weeks 1
• Symptoms progress or spread beyond the perianal region 1

Refer to psychiatry if:

• Severe anxiety/depression develops requiring specialized management 3, 4
• Patient develops obsessive behaviors around the sensation 3