The diameters and number of nerve fibers in spinal nerve roots

Liu, YongTao; Zhou, Xiao-Ji; Ma, Jun; Ge, Yali; Cao, Xiaojian

doi:10.1179/1079026814z.000000000273

Cited by 42 publications

(37 citation statements)

References 20 publications

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“…These motor fibers are probably also more sensitive to damage than sensory fibers, especially A-delta ones. 18 The diameter and the number of nerve fibers of each nerve root differs in cervical, thoracic and lumbar segments 38 and the better knowledge about preserved nerve fibers continuity provides basic data for future neuroanastomosis. 27 Preserved cutaneous SP proves that spinal cord circuit is functionally intact.…”

Section: Discussionmentioning

confidence: 99%

Preserved cutaneous silent period in cervical root avulsion

Vaško

Boček

Mencl

et al. 2015

The Journal of Spinal Cord Medicine

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Objective: Brachial plexus injuries are usually severe and involve the entire brachial plexus, sometimes occurring with root avulsions. Imaging and electrodiagnostic studies are an essential part of the lesion evaluation; however, the results sometimes show a discrepancy. The cutaneous silent period (SP) is a spinal inhibitory reflex mediated by small-diameter A-delta nociceptive fibers. The aim of the study was to determine if cutaneous SP testing may serve as a useful aid in evaluation of brachial plexus injury and/or in the diagnosis of root avulsion. Methods: In 19 patients with traumatic brachial plexus injury (15 males, age 18-62 years) we performed a clinical examination, CT myelography and neurophysiological testing. A needle EMG was obtained from muscles supplied by C5-T1 myotomes. Cutaneous SP was recorded after painful stimuli were delivered to the thumb (C6 dermatome), middle (C7) and little (C8) fingers while subjects maintained voluntary contraction of intrinsic hand muscles. Results: Electrodiagnostic and imaging studies confirmed root avulsion (partial or total) maximally involving C5, C6 roots in 12 patients, whereas only in 4 of them the cutaneous SP was partially absent. In the remaining subjects, the cutaneous SP was preserved. Conclusion: In brachial plexopathy even with plurisegmental root avulsion, the cutaneous SP was mostly preserved. This method cannot be recommended as a reliable test for diagnosis of single root avulsion; however, it can provide a quick physiological confirmation of functional afferent A-delta fibers through damaged roots and/or trunks. The clinicians may add this test to the diagnosis of spinal cord dysfunction.

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Section: Discussionmentioning

confidence: 99%

Preserved cutaneous silent period in cervical root avulsion

Vaško

Boček

Mencl

et al. 2015

The Journal of Spinal Cord Medicine

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“…Hairy skin on arms, trunk, and legs. The dorsal roots of the spinal cord contain 1-1.2 million fibers in total, ranging from large, medium, and small myelinated to unmyelinated nerve fibers (70,71). The region of skin innervated by all tactile afferents passing through a given dorsal root is known as a dermatome.…”

Section: Foot Solementioning

confidence: 99%

“…Fiber counts in individual dorsal roots can, therefore, be used to estimate the innervation of their associated dermatomes. For the estimates presented in this study, we follow the recent fiber counts in Liu et al (70). The territory of each dermatome is derived from illustrations in Grant and Anderson (72): the area of skin innervated by each dermatome is calculated as the sum of the areas covering the front and back of the body, respectively, assuming a total area of skin of 1.5 m 2 (73).…”

Section: Foot Solementioning

confidence: 99%

Tactile innervation densities across the whole body

Corniani

Saal

2020

Preprint

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The skin is our largest sensory organ and innervated by afferent fibers carrying tactile information to the spinal cord and onto the brain. The density with which different classes of tactile afferents innervate the skin is not constant but varies considerably across different body regions. However, precise estimates of innervation density are only available for some body parts, such as the hands, and estimates of the total number of tactile afferent fibers are inconsistent and incomplete. Here we reconcile different estimates and provide plausible ranges and best estimates for the number of different tactile fiber types innervating different regions of the skin, using evidence from dorsal root fiber counts, microneurography, histology, and psychophysics. We estimate that the skin across the whole body is innervated by approximately 230,000 tactile afferent fibers (plausible range: 200,000-270,000). 15% innervate the palmar skin of both hands and 19% the region surrounding the face and lips. Around 60% of all tactile fibers are slowly-adapting, while the rest are fastadapting. Innervation density correlates well with psychophysical spatial acuity across different body regions, and additionally, on hairy skin, with hair follicle density. Innervation density is also weakly correlated with the size of the cortical somatotopic representation, but cannot fully account for the magnification of the hands and the face. cutaneous afferent | mechanoreceptor | glabrous skin | hairy skin Correspondence: h.saal@sheffield.ac.uk Corniani et al. | bioRχiv | April 27, 2020 | 1-9

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“…The oblique course of the spinal nerve rootlets can cause retraction at mobile segments of the vertebral column. 10 The cervical segment of the vertebral column is mobile, thus the angle of the cervical spinal rootlets can change during flexion, extension, and lateral flexion of the neck. Therefore, all measurements on the cadaver were made in a standard position.…”

Section: The Angle Between the Cervical Spinal Rootlets And The Longimentioning

confidence: 99%

Morphometric Study of the Cervical Spinal Canal Content and the Vertebral Artery

Aydoğmuş

Çavdar

2020

Int J Spine Surg

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Background: The morphological features of the cervical spinal nerves (C1-C8), their dimensions, and their anatomical relations with the vertebral artery are important for safe spinal surgery. The aim of the present study is to give detailed morphological data of the region to avoid complications. Methods: Five formalin-fixed adult cadavers were studied. The cervical spinal nerves and the vertebral artery were exposed via the posterior approach, and detailed anatomy and morphometric measurements were evaluated. The following measurements were documented: angles between the spinal nerve and the spinal cord of C1 to C8, width of the C1 to C8 spinal nerves at their origin, distance of the spinal cord to the vertebral artery, number of dorsal rootlets, length of the dorsal root entry zone of C1 to C8, and distance between respective spinal nerves. Further, the average length and width of the transverse foramen were measured. Results: The average angle between the spinal cord and the spinal nerve within the vertebral canal ranged between 54 and 87 degrees and were most acute at C5 (54 degrees) compared to the rest of the cervical spinal nerves. The average width of the spinal nerves (mean 6 SD), was thickest at C5 (5.7 6 1.2 mm) and C6 (5.8 6 0.7 mm). The average largest distance between the vertebral artery and the spinal cord was at C2 (14.3 6 1.7 mm) and the smallest at C5 (7.3 6 0.9 mm) and C6 (7.3 6 2.2 mm) spinal levels. The number of dorsal rootlets was most numerous at C6 (8.25 6 0.6) and C7 (7.25 6 0.9). The dorsal root entry zone length was the largest at C5 (13.0 6 1.6 mm) and C6 (13.75 6 0.5 mm). The distance between respective spinal nerves was largest between C2 and C3 (11.8 6 2.2) and C7 and C8 (11.5 6 0.6). Conclusion: The knowledge of detailed anatomy of the cervical spine (C1-C8) and its relations with the vertebral artery will reduce the unwanted damage to the vital structures of the region.

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The diameters and number of nerve fibers in spinal nerve roots

Cited by 42 publications

References 20 publications

Preserved cutaneous silent period in cervical root avulsion

Preserved cutaneous silent period in cervical root avulsion

Tactile innervation densities across the whole body

Morphometric Study of the Cervical Spinal Canal Content and the Vertebral Artery

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