Long-Pulsed Nd:YAG vs Q-Switched Nd:YAG Laser Indications in Dermatology
Long-pulsed Nd:YAG laser is primarily indicated for vascular lesions and hair removal, while Q-switched Nd:YAG laser targets pigmented lesions including tattoos and benign melanocytic conditions. These two laser modalities operate on fundamentally different principles—pulse duration determines tissue selectivity—making them complementary rather than interchangeable tools in dermatologic practice.
Long-Pulsed Nd:YAG Laser (1064 nm) Indications
Hair Removal (Primary Indication)
- First-line treatment for Fitzpatrick skin types IV-VI due to longer wavelength providing deeper penetration with minimal epidermal melanin absorption, reducing pigmentary complication risk 1, 2
- For darker skin types (IV-VI): use 20-ms pulse duration with 25-40 J/cm² 1, 2
- For lighter skin types (I-III): use 10-mm spot size with 10-ms pulse duration and 35-50 J/cm² 1, 2
- Achieves 65-73% reduction in follicular activity across anatomic sites in randomized controlled trials 1, 2
- Requires 3-4 treatment sessions, though additional treatments provide more lasting follicular reduction 1, 2
- Clinical endpoint: delayed post-treatment perifollicular erythema and/or edema indicating follicular destruction 1, 2, 3
Vascular Lesions
- Spider angiomas: 100% marked improvement or clearance rate 4
- Facial telangiectasias: 97% marked improvement or clearance, though not first-choice for superficial facial vessels where depth is not a concern 4
- Leg telangiectasias: 80.8% marked improvement or clearance 4
- Port wine stains: 63.2% achieved >50% improvement 5
- Hemangiomas: 80.0% achieved >50% improvement 5
- Treatment typically requires 2 sessions at 4-week intervals, with 78.6% achieving excellent improvement (>75%) after second session 6
- Most common side effect is erythema (12.4%) 6
Hidradenitis Suppurativa
- Recommended for Hurley stage II-III disease based on RCT and case series data 7, 1
- Recommended for Hurley stage I disease based on expert consensus 7, 1
- Entire affected body region treated with active nodules double-pulsed in stacked fashion 7
- Dual mechanism: follicular destruction serves both hair removal and disease management 1
Q-Switched Nd:YAG Laser (1064 nm and 532 nm) Indications
Pigmented Lesions (Primary Indication)
- Tattoo removal: professional and traumatic tattoos 8
- Nevus of Ota 8
- Café-au-lait macules 8
- Lentigines 8
- The Q-switched mode delivers extremely short pulses (nanoseconds) that create photomechanical disruption of pigment particles while sparing surrounding tissue 8
Frequency-Doubled Mode (532 nm)
- When frequency-doubled to 532 nm, can treat superficial vascular lesions 8
- Also effective for red and orange tattoo pigments that don't respond to 1064 nm 8
Key Distinguishing Features
Pulse Duration Determines Target
- Long-pulsed (milliseconds): thermal coagulation of blood vessels and hair follicles through selective photothermolysis 4, 5, 6
- Q-switched (nanoseconds): photomechanical fragmentation of pigment particles 8
Clinical Pitfalls to Avoid
- Do not use long-pulsed Nd:YAG as first-line for superficial facial vessels—pulsed dye laser is superior when depth is not a concern 4
- Higher fluences (60-80 J/cm²) with longer pulse durations (50 msec) correlate with better hair removal outcomes but increased acute reactions including pain, erythema, and perifollicular edema 9
- Proper patient selection and tailoring fluence to skin type are the most critical factors for efficacy and tolerability 1, 2
Limited or Inappropriate Indications
- Cutaneous squamous cell carcinoma: Nd:YAG laser treatment reported in only single retrospective study with extremely limited experience precluding recommendation 7
- Bowen's disease: insufficient evidence available for laser treatment 7
- Infantile hemangiomas: pulsed dye laser preferred over Nd:YAG for early superficial lesions 7