title: Craniotomy: true sham for traumatic brain injury, or a sham of a sham?
abstract: Abstract Neurological dysfunction after traumatic brain injury (TBI) is caused by both the primary injury and a secondary cascade of biochemical and metabolic events. Since TBI can be caused by a variety of mechanisms, numerous models have been developed to facilitate its study. The most prevalent models are controlled cortical impact and fluid percussion injury. Both typically use "sham" (craniotomy alone) animals as controls. However, the sham operation is objectively damaging, and we hypothesized that the craniotomy itself may cause a unique brain injury distinct from the impact injury. To test this hypothesis, 38 adult female rats were assigned to one of three groups: control (anesthesia only); craniotomy performed by manual trephine; or craniotomy performed by electric dental drill. The rats were then subjected to behavioral testing, imaging analysis, and quantification of cortical concentrations of cytokines. Both craniotomy methods generate visible MRI lesions that persist for 14 days. The initial lesion generated by the drill technique is significantly larger than that generated by the trephine. Behavioral data mirrored lesion volume. For example, drill rats have significantly impaired sensory and motor responses compared to trephine or naïve rats. Finally, of the seven tested cytokines, KC-GRO and IFN-γ showed significant increases in both craniotomy models compared to naïve rats. We conclude that the traditional sham operation as a control confers profound proinflammatory, morphological, and behavioral damage, which confounds interpretation of conventional experimental brain injury models. Any experimental design incorporating "sham" procedures should distinguish among sham, experimentally injured, and healthy/naïve animals, to help reduce confounding factors.
authors.affiliation: Department of Neurology, Uniformed Services University of the Health Sciences, Silver Spring, Maryland, USA. jeffrey.cole@usuhs.mil
authors.forename: Jeffrey T
authors.initials: JT
authors.lastname: Cole
authors.forename: Angela
authors.initials: A
authors.lastname: Yarnell
authors.forename: William S
authors.initials: WS
authors.lastname: Kean
authors.forename: Eric
authors.initials: E
authors.lastname: Gold
authors.forename: Bobbi
authors.initials: B
authors.lastname: Lewis
authors.forename: Ming
authors.initials: M
authors.lastname: Ren
authors.forename: David C
authors.initials: DC
authors.lastname: McMullen
authors.forename: David M
authors.initials: DM
authors.lastname: Jacobowitz
authors.forename: Harvey B
authors.initials: HB
authors.lastname: Pollard
authors.forename: J Timothy
authors.initials: JT
authors.lastname: O'Neill
authors.forename: Neil E
authors.initials: NE
authors.lastname: Grunberg
authors.forename: Clifton L
authors.initials: CL
authors.lastname: Dalgard
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Frank
authors.forename: William D
authors.initials: WD
authors.lastname: Watson
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001930:Brain Injuries / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology; D002540:Cerebral Cortex / Q000293:injuries* / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology; D003399:Craniotomy; D016207:Cytokines / Q000378:metabolism; D005260:Female; D009682:Magnetic Resonance Spectroscopy; D023421:Models, Animal; D009048:Motor Skills / Q000502:physiology; D010919:Placebos; D051381:Rats; D017208:Rats, Wistar; D045442:Rotarod Performance Test
chemical_list: D016207:Cytokines; D010919:Placebos