C5 and C6 human dermatomes: a clinical, electromyographical, imaging and surgical findings

Dermátomos humanos C5 e C6: estudo clínico, eletromiográfico, de imagem e cirúrgico

C5 and C6 human dermatomes: a clinical, electromyographical, imaging and surgical findings

Dermátomos humanos C5 e C6: estudo clínico, eletromiográfico, de imagem e cirúrgico

Antonio Tadeu de Souza Faleiros^I; Luiz Antonio de Lima Resende^I; Marco Antonio Zanini^I; Heloisa Amélia de Lima Castro^II; Roberto Colichio Gabarra^I

^IDepartment of Neurology, Psycology and Psychiatry, Botucatu Medical School, São Paulo State University (UNESP), Botucatu SP, Brazil

^IIDepartment of Morphology, Piracicaba Dental School, UNICAMP, Campinas SP, Brazil

ABSTRACT

There is substantial controversy in literature about human dermatomes. In this work, C5 and C6 superior limb dermatomes were studied. The method consisted of comparing clinical signs and symptoms with conduction studies, electromyographical data, neurosurgical findings, and imaging findings obtained by computerized tomography (CT) or magnetic resonance imaging (MRI), for each patient. Data analysis from superior members in 18 patients suggests that C5 is located in the lateral aspect of the shoulder and arm, and C6 in the lateral aspect of the forearm and 1^st, 2^nd, and 3^rd fingers. To our knowledge this is the first time that C5 and C6 human dermatomes have been studied by all the following methods together: clinical, electromyographical, CT and MR imaging, and surgical findings.

Key words: eletromyography, human dermatome, imaging, superior member.

RESUMO

Há controvérsias na literatura sobre os dermátomos humanos. Neste estudo os dermátomos do membro superior C5 e C6 foram analisados. O método consistiu em comparar os sinais e sintomas com achados eletromiográficos, de imagem e achados cirúrgicos. Análise dos dados do membro superior de 18 pacientes sugere que o dermátomo C5 esteja localizado na região lateral do ombro e braço, e o dermátomo C6 na região lateral do antebraço e 1º, 2º e 3º dedos da mão. Este é o primeiro estudo em que os dermátomos C5 e C6 foram avaliados pelos dados clínicos, eletromiográficos, de imagem e achados cirúrgicos.

Palavras-chave: dermátomo humano, eletromiografia, imagem, membro superior.

The C5 and C6 human anatomical territories are frequently found to be compromised in neurology clinic, mainly after traumas, but several controversies exist about C5 and C6 human dermatomes. For Bing¹, Platzer² Duss³, and Carpenter⁴ C5 is represented in a small restricted area of the lateral aspect of the proximal arm, but for Testut⁵ Déjérine⁶, Brain⁷, Bickerstaff⁸, Patten⁹, Spalteholz¹⁰, Adams¹¹, and Noback¹², it is represented in a more extensive area, the whole lateral aspect of the arm; for Barraquer, an extensive area of the lateral aspect of the arm and forearm, includind the thumb¹³; for Elliot¹⁴ and Gardner¹⁵ it is similar but the thumb is not included; for Yokochi¹⁶, Brodal¹⁷, Keegan-Garret¹⁸, DeJong¹⁹, and Curtis²⁰ it is represented in a more extensive anterior area of arm and forearm, but there is no superposition between the maps of DeJong¹⁹, Brodal¹⁷, and Yokochi¹⁶.

First year students in our medical school are completely confused by this because these two dermatomes are presented differently in all our clinical and anatomical text books. We believe that several of these text book interpretations were not based on the modern techniques that allow comparison of clinical symptoms with electromyographical data, neurosurgery findings, and CT and MRI images.

Our objective is to furnish probable C5 and C6 human dermatome maps obtained by comparing clinical, electromyographical, neurosurgical, and CT and MRI data.

METHOD

This study includes patients with a clinical diagnosis of cervical radiculopathy seen between 1992 and 2005 at our university hospital. After approval from the Ethics Committee on Human Research, patients with clinical diagnosis of C5 and/or C6 cervical radyculopathy were included in accordance to the following criteria:

I - Conduction studies and electromyographical diagnosis of C5 and/or C6 radyculopathy were in accordance with electromyography text-books^21,22 and included: A) normal latencies, amplitudes, and conduction velocities of the ulnar, median, and radial nerves in the symptomatic arm coexisting with neurogenic electromyographical findings in the deltoideus and supraspinatus muscle for C5 diagnosis, or in the biceps brachialis and coracobrachialis muscle for C6 diagnosis. B) Neurogenic findings were: spontaneous activity, with positive sharp waves or fibrillations and/or muscle at rest fasciculation; increased duration and amplitude neurogenic motor unit potentials with mild effort; reduced recruitment and incomplete interference pattern at maximum muscle contraction. C) Clinical romboideus muscular weakness was an additional criterion for C5 diagnosis.

II - Surgical findings: Several patients with unsuccessful clinical treatment required surgery for cervical root decompression. These surgical anatomical data were analyzed.

III - Imaging diagnosis of C5 and/or C6 radyculopathy: All patients had imaging diagnosis of compressive radyculopathy by CT or MRI.

RESULTS

A total of 18 patients were analyzed.

Group 1 - Ten patients with associated C5 and C6 cervical root compression (6 with successful clinical treatment - without surgery; 4 with unsuccessful clinical treatment, submitted to surgery). The combined C5 and C6 clinical symptoms territory for these 10 patients was on the lateral aspect of shoulder, arm, forearm, and I, II, and III fingers (Fig 1).

Group 2 - Six patients with isolated C5 compression (3 with successful clinical treatment, 3 with unsuccessful clinical treatment, submitted to surgery). The C5 clinical symptoms territory for these 6 patients was on the lateral aspect of shoulder and arm (Fig 2).

Group 3 - Two with isolated C6 compression (1 submitted to clinical treatment, 1 with unsuccessful clinical treatment, submitted to surgery). The C6 clinical symptoms territory for these 2 patients was on the lateral aspect of the forearm and I, II, and III fingers (Fig 3).

DISCUSSION

There are several theory problems for dermatome definitions in humans. The pioneer study on dermatomes was by Sherrington²³ and, more recently, by Kirk and Denny-Brown²⁴, both with monkeys. However, it is difficult to rely on animal dermatome data when dealing with man.

For classical anatomic authors like Testut and Latarjet⁵, the main limitation was defining dermatomes from postmortem studies. In classical neurologic semiology, at the time of Déjérine⁶, the main limitation was the lack of conduction studies, electromyography, and imaging.

The first human dermatomes were postulated by clinical data from patients with Herpes zoster²⁵, but in most patients herpetic infection is not restricted, involving more cranial or distal spinal segments^26,27 making definition of a specific dermatome impossible. There are published Herpes zoster cases showing impairment of 2 or 3 adjacent dermatomes in 7 distinct regions of the human body²⁸. New paravertebral anesthetic block techniques have recently been developed but defining an isolated dermatome was still not possible because the anesthetic drugs were diffused in the cerebrospinal fluid^29-32.

Our study is simple: comparison of clinical symptoms, electromyography, imaging, and surgical findings enabling us to deduce the probable location for human C5 and C6 dermatomes. We concluded that the C5 human dermatome is probably on lateral aspect of the shoulder and arm; and the C6 human dermatome is probably on the lateral aspect of the forearm, and I, II, and III fingers.

Received 18 August 2008, received in final form 12 November 2008. Accepted 2 February 2009.

Dr. Marco Antonio Zanini - Departamento de Neurologia e Psiquiatria / Faculdade de Medicina de Botucatu / UNESP / Rubião Jr S/N - Caixa Postal: 540 - 18618-970 Botucatu SP - Brasil. E-mail: [e-mail]

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Publication Dates

• Publication in this collection
  05 June 2009
• Date of issue
  June 2009

History

• Accepted
  02 Feb 2009
• Received
  12 Nov 2008