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Correspondence |

Recovery of Consciousness After Head InjuryRecovery of Consciousness After Head Injury FREE TO VIEW

Marco Gemma, MD; Luigi Beretta, MD; Maria Rosa Calvi, MD
Author and Funding Information

From the Anesthesia and Intensive Care Department, San Raffaele Scientific Institute, San Raffaele Hospital, Vita-Salute San Raffaele University.

Correspondence to: Marco Gemma, MD, Anesthesia and Intensive Care Department, San Raffaele Scientific Institute, San Raffaele Hospital, Vita-Salute San Raffaele University, Via Olgettina 60, 20132 Milan, Italy; e-mail: gemma.marco@hsr.it


Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2014;145(3):664-665. doi:10.1378/chest.13-2611
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To the Editor:

Luce1 is to be commended for his excellent review on chronic disorders of consciousness following coma that recently published in CHEST (October 2013). Nevertheless, we wish to point out that, in our opinion, the author is inaccurate in stating that “coma following TBI [traumatic brain injury] usually is manifested pathologically by diffuse axonal injury, which also is called traumatic injury, involving the cerebral cortices and brain stem.”1

The mechanisms involved in TBI and coma are actually complex and often multifactorial. Focal lesions (extradural and subdural hematomas, intraparenchymal hematomas and contusions), diffuse lesions (swelling, diffuse axonal injury [DAI], posttraumatic subarachnoid hemorrhage), and biochemical derangements can act as independent or associated causes of coma after TBI. The variety of lesions associated with TBI is compounded by the Marshall classification of head injury based on CT scanning.2 These conditions cause coma when they affect brain perfusion and cortical or brain stem activity.

DAI is only one possible physiopathologic mechanism causing coma after TBI and typically occurs during high-speed impact trauma causing rotational acceleration. This causes axonal damage, as the axons are torn or stretched, thus, impairing axoplasmic transport and, ultimately, the electrical neural network.3

It should be noted that, when dealing with DAI, CT scanning can offer some clues to diagnosis,4 but it is often inaccurate in identifying injuries. MRI can clearly detect DAI deep lesions. Moreover, MRI is potentially useful as a clue to prognosis because it assesses the severity of DAI, which is classified as mild (as only corticosubcortical lesions are apparent), moderate (as corpus callosum is involved), or severe (as brain stem is involved).5

References

Luce JM. Chronic disorders of consciousness following coma: part one: medical issues. Chest. 2013;144(4):1381-1387. [CrossRef] [PubMed]
 
Marshall LF, Marshall SB, Klauber MR. A new classification of head injury based on computerized tomography. J Neurosurg. 1991;75(suppl):S14-S20.
 
Gennarelli TA, Thibault LE, Adams JH, Graham DI, Thompson CJ, Marcincin RP. Diffuse axonal injury and traumatic coma in the primate. Ann Neurol. 1982;12(6):564-574. [CrossRef] [PubMed]
 
Beretta L, Anzalone N, Dell’Acqua A, Calvi MR, Gemma M. Post-traumatic interpeduncular cistern hemorrhage as a marker for brainstem lesions. J Neurotrauma. 2010;27(3):509-514. [CrossRef] [PubMed]
 
Calvi MR, Beretta L, Dell’Acqua A, Anzalone N, Licini G, Gemma M. Early prognosis after severe traumatic brain injury with minor or absent computed tomography scan lesions [published correction appears inJ Trauma. 2011;70(6):1582]. J Trauma. 2011;70(2):447-451. [CrossRef] [PubMed]
 

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References

Luce JM. Chronic disorders of consciousness following coma: part one: medical issues. Chest. 2013;144(4):1381-1387. [CrossRef] [PubMed]
 
Marshall LF, Marshall SB, Klauber MR. A new classification of head injury based on computerized tomography. J Neurosurg. 1991;75(suppl):S14-S20.
 
Gennarelli TA, Thibault LE, Adams JH, Graham DI, Thompson CJ, Marcincin RP. Diffuse axonal injury and traumatic coma in the primate. Ann Neurol. 1982;12(6):564-574. [CrossRef] [PubMed]
 
Beretta L, Anzalone N, Dell’Acqua A, Calvi MR, Gemma M. Post-traumatic interpeduncular cistern hemorrhage as a marker for brainstem lesions. J Neurotrauma. 2010;27(3):509-514. [CrossRef] [PubMed]
 
Calvi MR, Beretta L, Dell’Acqua A, Anzalone N, Licini G, Gemma M. Early prognosis after severe traumatic brain injury with minor or absent computed tomography scan lesions [published correction appears inJ Trauma. 2011;70(6):1582]. J Trauma. 2011;70(2):447-451. [CrossRef] [PubMed]
 
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