What could be causing a pulsating sensation in the perineum area, similar to a pulse feeling?

Pulsating Sensation in the Perineum: Differential Diagnosis and Management

A pulsating sensation in the perineum most commonly represents normal vascular pulsations from the internal pudendal artery or its branches, but requires urgent evaluation to exclude serious neurological or infectious conditions, particularly cauda equina syndrome and Fournier's gangrene.

Immediate Red Flag Assessment

You must first exclude life-threatening conditions that present with perineal sensations:

Cauda Equina Syndrome (CES)

• Any subjective perineal sensory changes—including pulsating or abnormal sensations—combined with bilateral leg symptoms demands emergency MRI 1, 2
• Red flag symptoms requiring immediate action include:
  • Bilateral radicular leg pain or weakness 1, 2
  • New urinary difficulties (hesitancy, poor stream, urgency) with preserved control 1
  • Any subjective or objective loss of perineal sensation 1, 2
• Do not wait for urinary retention or complete perineal anesthesia—these are late "white flag" signs indicating irreversible damage 1, 2
• MRI must be performed emergently if any red flags are present, as symptoms typically progress gradually over weeks to months 2

Fournier's Gangrene

• Maintain high suspicion if the patient has diabetes, immunocompromise, or obesity 3, 4
• Early presentation may be insidious with undiagnosed perineal pain in up to 40% of cases 4
• Look for scrotal/perineal erythema, edema, tenderness, or foul-smelling discharge 4
• This necrotizing infection has 20-50% mortality and requires immediate surgical debridement 4

Benign Neurological Causes

If red flags are absent, consider pudendal nerve-related conditions:

Pudendal Nerve Entrapment (Alcock's Canal Syndrome)

• The hallmark is burning pain or paresthesias (which can feel pulsating) that worsen with sitting and improve when standing 5, 6, 7
• The pudendal nerve controls perineal sensation and can be compressed at three key points: between sacrotuberous and sacrospinous ligaments, at the falciform process, or in Alcock's canal 5
• Diagnosis requires clinical criteria (Nantes criteria): characteristic positional pain pattern, neurological exam findings, and temporary response to nerve block 5
• Electrodiagnostic testing showing prolonged pudendal nerve distal motor latency confirms the diagnosis 7
• Treatment progresses from medical management and physical therapy to CT-guided infiltrations, with surgery reserved as last resort (75% success rate) 5, 6

Other Pudendal Neuropathies

• Consider history of bicycle riding, perineal trauma, or prolonged sitting 7
• Spinal cord lesions (particularly conus medullaris tumors) can cause perineal dysesthesias 6
• Sacral meningoradiculitis or pudendal nerve neuritis are less common causes 6

Functional Pelvic Floor Disorders

When organic disease is excluded, consider:

Levator Ani Syndrome and Related Conditions

• Chronic perineal pain without underlying organic disease after thorough exclusion of structural pathology 8
• Neuromuscular disorders of the pelvic floor can produce various sensory phenomena including pain and abnormal sensations 8
• Requires thorough history, physical examination including digital rectal exam to assess pelvic floor muscle tone, and specialized investigations 8

Normal Vascular Pulsations

• The internal pudendal artery and its branches supply the perineum and can produce palpable pulsations 5
• This is a diagnosis of exclusion after ruling out pathological causes
• More likely if the sensation is rhythmic, corresponds to heart rate, and has no associated symptoms

Diagnostic Algorithm

1. Screen for CES red flags (bilateral symptoms, urinary changes, perineal sensory changes) → Emergency MRI if present 1, 2
2. Examine for infection signs (erythema, edema, systemic illness) → Immediate surgical consultation if Fournier's suspected 4
3. Assess positional nature of symptoms (worse sitting, better standing) → Consider pudendal nerve entrapment 5, 6, 7
4. Perform neurological examination including perineal sensation, anal tone, and lower extremity strength/reflexes 1
5. If examination normal and no red flags, consider electrophysiological testing of pudendal nerve if symptoms persist 6

Critical Pitfalls to Avoid

• Never dismiss bilateral leg symptoms or new urinary changes as benign—these demand emergency imaging 1, 2
• Perineal sensory testing is subjective and subtle impairment is easily missed 1
• In obese patients, examination is limited and requires higher index of suspicion for serious pathology 4
• Do not perform unnecessary surgical procedures for functional pain syndromes without proper diagnosis 8