Residency · Residency · Chronic Pain Management

Peripheral Nerve Blocks for Chronic Pain

Introduction

Peripheral nerve blocks occupy an important position in the chronic pain management armamentarium, offering targeted diagnostic and therapeutic interventions for regional pain syndromes. Unlike the acute perioperative setting where these blocks provide short-term surgical anesthesia, chronic pain applications focus on diagnostic confirmation of a specific nerve as a pain generator, therapeutic relief through local anesthetic and corticosteroid combinations, and potentially pulsed radiofrequency neuromodulation for longer-lasting benefit. This lecture covers four key peripheral nerve blocks: occipital nerve blocks, suprascapular nerve blocks, lateral femoral cutaneous nerve blocks, and ilioinguinal/iliohypogastric nerve blocks.

Occipital Nerve Blocks

Anatomy

The greater occipital nerve (GON) arises from the dorsal ramus of C2 (with contributions from C3), pierces the semispinalis capitis and trapezius muscles, and becomes subcutaneous approximately 2 cm lateral to the external occipital protuberance at the level of the superior nuchal line. The lesser occipital nerve (LON) originates from the ventral rami of C2-C3, courses along the posterior border of the sternocleidomastoid, and innervates the lateral scalp posterior to the ear. The third occipital nerve (TON), from the dorsal ramus of C3, innervates the suboccipital region and the C2-3 facet joint.

Indications

Occipital nerve blocks are indicated for occipital neuralgia (sharp, shooting, or electric pain in the distribution of the GON or LON), cervicogenic headache (headache originating from cervical spine pathology with referred pain to the occiput), migraine (as adjunctive therapy, with multiple studies demonstrating benefit for both prevention and acute treatment), and cluster headache (adjunctive therapy during cluster periods).

Technique

For the landmark-based approach, the GON is palpated approximately 2 cm lateral to the external occipital protuberance at the superior nuchal line, often adjacent to a palpable occipital artery pulse. A 25-27 gauge needle is inserted at this point, and after negative aspiration, 2-3 mL of local anesthetic (0.5% bupivacaine or 2% lidocaine) with or without corticosteroid (dexamethasone 4 mg or methylprednisolone 40 mg) is injected. For the ultrasound-guided technique, a high-frequency linear transducer is placed transversely at the superior nuchal line, and the GON is visualized as a small hypoechoic structure medial to the occipital artery between the semispinalis capitis and trapezius. The LON is blocked at the posterior border of the sternocleidomastoid at the level of the superior nuchal line.

Evidence

Ambrosini et al. (2005) showed that GON block with betamethasone reduced migraine frequency and attack severity at 30 and 60 days. Inan et al. (2015) conducted an RCT of GON block versus saline for chronic migraine that demonstrated significant pain reduction at 1 month. Multiple systematic reviews support GON block as a Level B recommendation for migraine prophylaxis.

<image>Posterior view anatomical illustration of the occipital region showing the course of the greater occipital nerve (GON) emerging through the semispinalis capitis and trapezius aponeurosis approximately 2 cm lateral to the external occipital protuberance. The lesser occipital nerve (LON) is shown ascending along the posterior border of the sternocleidomastoid. The third occipital nerve (TON) is depicted medial to the GON. The occipital artery is shown running parallel to the GON. Injection sites for each nerve are marked with an X. An ultrasound probe positioning inset shows transverse placement at the superior nuchal line with a corresponding sonographic image identifying the GON, occipital artery, semispinalis capitis, and trapezius muscle.</image>

Suprascapular Nerve Block

Anatomy

The suprascapular nerve arises from the upper trunk of the brachial plexus (C5-C6, occasionally C4) and passes through the suprascapular notch beneath the transverse scapular ligament (the suprascapular artery passes above the ligament). It provides motor innervation to the supraspinatus and infraspinatus muscles and sensory innervation to approximately 70% of the glenohumeral joint, covering the posterior and superior joint capsule, the acromioclavicular joint, and the subacromial bursa.

Indications

Suprascapular nerve block is indicated for adhesive capsulitis (frozen shoulder), where significant evidence supports the block for pain relief and improved range of motion. Other indications include chronic shoulder pain from rotator cuff disease, glenohumeral osteoarthritis, and postoperative shoulder pain; cancer pain from Pancoast tumor or brachial plexopathy; and hemiplegic shoulder pain following stroke.

Technique

For the landmark-based approach, the suprascapular notch is located by bisecting the spine of the scapula and directing the needle approximately 1 cm superiorly toward the floor of the suprascapular fossa. The preferred ultrasound-guided technique uses a high-frequency linear transducer placed in the coronal oblique plane over the suprascapular fossa, with the suprascapular nerve visualized at the floor of the fossa beneath the transverse scapular ligament. An injection of 4-5 mL of local anesthetic (0.5% bupivacaine) with or without corticosteroid is delivered. Pulsed radiofrequency of the suprascapular nerve has been described for longer-lasting relief of 3-6 months.

Evidence

Shanahan et al. (2003) conducted an RCT demonstrating that suprascapular nerve block significantly reduced pain and improved shoulder function in adhesive capsulitis. Abdelshafi et al. (2008) compared suprascapular nerve block with intra-articular injection and showed superior results for the nerve block in chronic shoulder pain. Systematic reviews support suprascapular nerve block as a well-established intervention for chronic shoulder pain of multiple etiologies.

Lateral Femoral Cutaneous Nerve Block

Anatomy

The lateral femoral cutaneous nerve (LFCN) arises from the dorsal divisions of L2-L3 and exits the pelvis near the anterior superior iliac spine (ASIS), typically passing medial to the ASIS and beneath (or through) the inguinal ligament. Anatomic variability is significant — the nerve may pass over, through, or beneath the inguinal ligament and may be located up to 2 cm medial or inferior to the ASIS. It provides purely sensory innervation to the anterolateral thigh.

Indications

The primary indication is meralgia paresthetica, an entrapment neuropathy of the LFCN causing burning pain, paresthesia, and numbness over the anterolateral thigh. The block serves for diagnostic confirmation before considering surgical decompression or neurolysis. Common etiologies include obesity, tight clothing or belts, prolonged hip flexion (surgical positioning), diabetes, and pregnancy.

Technique

The preferred ultrasound-guided technique uses a high-frequency linear transducer placed inferior and medial to the ASIS. The LFCN is identified as a small hyperechoic structure between the sartorius and tensor fasciae latae muscles, superficial to the iliacus, within a fibrous compartment. An injection of 5-8 mL of local anesthetic (0.5% bupivacaine) with or without corticosteroid is delivered. The landmark-based approach involves injecting 2 cm medial and 2 cm inferior to the ASIS using a fan technique, though this is less reliable due to anatomic variability.

Evidence

Karkare et al. (2006) described the ultrasound-guided technique with improved accuracy compared to the landmark approach. Treatment is primarily diagnostic and therapeutic; patients who respond to blocks but relapse may benefit from surgical decompression or pulsed radiofrequency.

<image>Anterior view anatomical illustration of the inguinal region showing the lateral femoral cutaneous nerve (LFCN) emerging from the pelvis medial to the anterior superior iliac spine (ASIS) and passing beneath the inguinal ligament. The nerve's course between the sartorius and tensor fasciae latae muscles is depicted, with its branching pattern over the anterolateral thigh highlighted. An inset shows the ultrasound transducer position and corresponding sonographic image with the LFCN identified as a hyperechoic fascicle between the sartorius and tensor fasciae latae, superficial to the iliacus muscle. The ASIS, inguinal ligament, and femoral neurovascular bundle (positioned more medially) are labeled.</image>

Ilioinguinal and Iliohypogastric Nerve Blocks

Anatomy

The ilioinguinal nerve (L1) and iliohypogastric nerve (T12-L1) arise from the lumbar plexus and course along the abdominal wall between the internal oblique and transversus abdominis muscles. They provide sensory innervation to the lower abdominal wall, inguinal region, and proximal medial thigh/genital area. The ilioinguinal nerve enters the inguinal canal and emerges through the superficial inguinal ring. Both nerves are at risk of injury during inguinal hernia repair, appendectomy, Pfannenstiel incision, and other lower abdominal surgeries.

Indications

The most common indication is post-herniorrhaphy inguinal pain (ilioinguinal neuralgia) — nerve entrapment or injury following inguinal hernia repair. Other indications include chronic lower abdominal wall pain following Cesarean section, appendectomy, or other lower abdominal procedures; groin pain of neural origin unresponsive to conservative management; and diagnostic block before surgical neurectomy.

Technique

The preferred ultrasound-guided technique uses a high-frequency linear transducer placed at the ASIS and moved medially along the line between the ASIS and the umbilicus. The nerves are identified in the fascial plane between the internal oblique and transversus abdominis muscles, with the ilioinguinal nerve typically found approximately 2-3 cm medial to the ASIS. An injection of 5-10 mL of local anesthetic (0.5% bupivacaine) with or without corticosteroid is delivered in the fascial plane (a TAP block variant targeting these specific nerves). The landmark-based approach involves injecting 2 cm medial and 2 cm inferior to the ASIS, directing the needle to pop through the external and internal oblique aponeuroses.

Evidence

Bischoff et al. (2012) published a systematic review of ilioinguinal and iliohypogastric nerve blocks for chronic post-herniorrhaphy pain that showed moderate evidence for diagnostic and therapeutic benefit. Patients with consistent relief from diagnostic blocks who require repeated injections may be candidates for surgical neurectomy or pulsed radiofrequency ablation. Cryoanalgesia of the ilioinguinal nerve has also been described with promising results for refractory cases.

General Principles for Peripheral Nerve Blocks in Chronic Pain

Diagnostic blocks should always precede any destructive or long-term intervention, as concordant pain relief confirms the nerve as the pain generator. Ultrasound guidance has improved accuracy, reduced complications, and decreased required volumes for all peripheral nerve blocks. Corticosteroid additives (dexamethasone, triamcinolone, methylprednisolone) may prolong the duration of relief beyond the local anesthetic effect. Pulsed radiofrequency (42 degrees Celsius, 120 seconds, 2-3 cycles) applied to peripheral nerves provides neuromodulation without neurodestructive injury and may extend relief for 3-6 months. Serial blocks with diminishing intervals of relief suggest the need for a definitive intervention such as surgical neurectomy, peripheral nerve stimulation, or cryoablation.

Clinical Pearls

For occipital nerve blocks, always palpate for the occipital artery pulse as a reliable landmark for the GON — the nerve runs medial to or immediately adjacent to the artery. Suprascapular nerve block provides excellent analgesia for chronic shoulder conditions and is underutilized; it blocks 70% of glenohumeral joint innervation without motor blockade of the arm. In meralgia paresthetica, always assess for reversible causes (weight loss, belt modification, medication review) before pursuing interventional treatment. Post-herniorrhaphy pain with a positive ilioinguinal nerve block is one of the best-supported indications for surgical neurectomy when blocks provide consistent but temporary relief. The exact duration and percentage of pain relief following diagnostic blocks should always be documented, as this information is critical for decision-making regarding definitive procedures.

References

1. Ambrosini A, Vandenheede M, Rossi P, et al. Suboccipital injection with a mixture of rapid- and long-acting steroids in cluster headache: a double-blind placebo-controlled study. Pain. 2005;118(1-2):92-96.
2. Shanahan EM, Ahern M, Smith M, et al. Suprascapular nerve block (using bupivacaine and methylprednisolone) in chronic shoulder pain. Ann Rheum Dis. 2003;62(5):400-406.
3. Bischoff JM, Koscielniak-Nielsen ZJ, Kehlet H, Werner MU. Ultrasound-guided ilioinguinal/iliohypogastric nerve blocks for persistent inguinal postherniorrhaphy pain: a randomized, double-blind, placebo-controlled, crossover trial. Anesth Analg. 2012;114(6):1323-1329.
4. Narouze S, Benzon HT, Provenzano D, et al. Interventional spine and pain procedures in patients on antiplatelet and anticoagulant medications: guidelines from the American Society of Regional Anesthesia and Pain Medicine. Reg Anesth Pain Med. 2015;40(3):182-212.

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