The triangular area between the greater, lesser, and third occipital nerves and its possible clinical significance.

PURPOSE: Occipital Neuralgia (ON) is defined as a unilateral or bilateral pain in the posterior area of the scalp occurring in the distribution area or areas of the greater occipital nerve (GON), lesser occipital nerve (LON), and/or third occipital nerve (TON). In the present study, the purpose was to show the possible importance of the triangular area (TA) in nerve block applied in ON by measuring the TA between GON, TON, and LON. METHODS: A total of 24 cadavers (14 males, 10 females) were used in the present study. The suboccipital region was dissected, revealing the points where the GON and TON pierced the trapezius muscle and superficial area, and the point where the LON left the sternocleidomastoid muscle from its posterior edge and was photographed. The area of the triangle between the superficial points of these three nerves and the center of gravity of the triangle (CGT) were determined by using the Image J Software and the results were analyzed statistically. RESULTS: The mean TA values were 952.82 ± 313.36 mm2 and 667.55 ± 273.82 mm2, respectively in male and female cadavers. Although no statistically significant differences were detected between the sides (p > 0.05), a statistically significant difference was detected between the genders (p < 0.05). The mean CGT value was located approximately 5 cm below and 3-3.5 cm laterally from the external occipital protuberance in both genders and sides. CONCLUSION: In ON that has more than one occipital nerve involvement, all occipital nerves can be blocked by targeting TA with a single occipital nerve block, and thus, the side effects that may arise from additional blocks can be reduced. The fact that there was a statistically significant difference according to the genders in the TA suggests that different block amounts can be applied according to gender.

Morphological and morphometric anatomy of the lesser occipital nerve and its possible clinical relevance.

The lesser occipital nerve (LON) has one of the most variations among occipital nerves. We aimed to investigate morphological and morphometric features of LON. A total of 24 cadavers, 14 males (58%) and 10 females (42%), were dissected bilaterally. LON was classified into 3 types. The number of branches and the perpendicular distances of the point where LON emerged from the posterior border of sternocleidomastoid muscle to vertical and transverse lines passing through external occipital protuberance were determined. The shortest distance between LON and great auricular nerve (GAN), and linear distance of LON to its branching point were measured. The most common variant was Type 1 (30 sides, 62.5%), followed by Type 2 (12 sides, 25%) and Type 3 (6 sides, 12.5%), respectively. In males, Type 1 (22 sides, 78.6%) was the most common, while Type 1 (8 sides, 40%) and Type 2 (8 sides, 40%) were equally common and the most common in females. On 48 sides, 2-9 branches of LON were observed. The perpendicular distance of said point to vertical and transverse lines was meanly 63.69 ± 11.28 mm and 78.83 ± 17.21 mm, respectively. The shortest distance between LON and GAN was meanly 16.62 ± 10.59 mm. The linear distance of LON to its branching point was meanly 31.24 ± 15.95 mm. The findings reported in this paper may help clinicians in estimating the location of the nerve and/or its branches for block or decompression surgery as well as preservation of LON during related procedures.

"A comprehensive study of the potential compression points of the third occipital nerve and its possible clinical interests".

BACKGROUND: The anatomical features of the third occipital nerve (TON) are the least studied among the occipital nerves. This study aimed to analyze the anatomical features and potential compression points of the TON. METHODS: The posterior neck and scalp of 39 cadavers were dissected. The TON was carefully followed from the emerging point from C2-C3 vertebrae distally. Its muscular investments were detected. The determined points were marked superficially and measured according to external occipital protuberance with the Image J Software program. RESULTS: The TON revealed 4 different potential entrapment points along its course. The most proximal point was between the C2-C3 vertebrae. The second and third points were at their piercing points of semispinalis capitis and splenius capitis muscles, respectively. The final point was at its penetrating point of the trapezius muscle. Additionally, TON did not pierce the semispinalis capitis muscle on 6 sides and pierced this muscle from 3 different points by splitting into 3 branches on 1 side. Moreover, on 5 sides, the TON split into two branches and perforated the splenius capitis muscle from two different points. CONCLUSION: There were 4 potential compression points regarding the TON. These entrapment points and variations of TON in this study may play a significant role in understanding the reason for TON-related headaches and the treatment of headaches caused by TON.