Where are the occipital nerves located for evaluation?

Anatomical Location of Occipital Nerves for Clinical Evaluation

The occipital nerves are best located for clinical evaluation at specific anatomical landmarks: the greater occipital nerve is approximately 3.8 cm lateral to the midline (external occipital protuberance), the lesser occipital nerve emerges at the posterior border of the sternocleidomastoid muscle, and the third occipital nerve is found about 3 mm lateral to the external occipital protuberance. 1, 2

Greater Occipital Nerve (GON)

• Located approximately 3.8 cm (range 1.5-7.5 cm) lateral to a vertical line through the external occipital protuberance 1
• Found at approximately 41% of the distance along the intermastoid line (measured from medial to lateral) 1
• Located at approximately 22% of the distance between the external occipital protuberance and the mastoid process 1
• The subcutaneous piercing point is most reliably found at the medial trisection point of a line connecting the external occipital protuberance and mastoid process 3
• When performing nerve blocks, injections should be placed inferior and lateral to this trisection point for highest success rate 3

Lesser Occipital Nerve (LON)

• Emerges at the posterior border of the sternocleidomastoid muscle 4
• Can be found where it leaves the sternocleidomastoid muscle at its posterior edge 4
• Forms part of a triangular area with the GON and TON that can be targeted for nerve blocks 4

Third Occipital Nerve (TON)

• Located approximately 3 mm lateral to the external occipital protuberance 2
• Small branches may cross the midline and communicate with the contralateral TON inferior to the external occipital protuberance in 66.7% of cases 2
• The TON trunk becomes subcutaneous at a mean of 5 cm inferior to the external occipital protuberance 2
• Intimately related to the nuchal ligament in its course 2

Triangular Area Between Occipital Nerves

• The triangular area between GON, LON, and TON has clinical significance for nerve blocks 4
• The center of gravity of this triangle is located approximately 5 cm below and 3-3.5 cm laterally from the external occipital protuberance 4
• This area is significantly larger in males (952.82 ± 313.36 mm²) than females (667.55 ± 273.82 mm²) 4
• Targeting this triangular area with a single block can affect all three occipital nerves simultaneously 4

Clinical Evaluation Technique

• For GON evaluation, palpate one thumb's breadth (approximately 2 cm) lateral to the external occipital protuberance and 2 cm inferior 1
• For TON evaluation, examine along the nuchal ligament, approximately 5 cm inferior to the external occipital protuberance 2
• For LON evaluation, trace the posterior border of the sternocleidomastoid muscle 4
• When evaluating for occipital neuralgia, assess all three nerves as the condition can involve any or all of these nerves 5

Imaging Considerations

• MRI is the preferred imaging modality for evaluating occipital nerves and related pathology 5
• Thin-section MRI protocols should be used when evaluating the occipital nerves 5
• Ultrasound is not routinely used in the initial evaluation of these nerves 5

Clinical Pearls

• The occipital nerves supply the sternocleidomastoid and trapezius muscles; weakness or atrophy of these muscles may indicate nerve pathology 5
• Occipital nerve blocks can be both diagnostic and therapeutic for occipital neuralgia 6
• When performing occipital nerve blocks for multiple nerve involvement, targeting the triangular area between the three nerves may reduce the need for multiple injections 4