The Japanese journal of neuropsychology

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ArticleTitle	Early computed tomographic and magnetic resonance imagings in patients with moderate to severe head injury: diagnostic limitations and pitfalls
Language	J
AuthorList	Hiroshi Nakamura¹⁾, Akihiro Miyata¹⁾, Yorio Koguchi²⁾, Yukiko Satoh³⁾, Shigeki Kobayashi¹⁾
Affiliation	¹⁾Department of Neurosurgery, Chiba Emergency Medical Center ²⁾Department of Neurology, Chiba Emergency Medical Center ³⁾Speech-Language-Hearing Therapist, Chiba Emergency Medical Center
Publication	Japanese Journal of Neuropsychology: 27 (2), 99-109, 2011
Received
Accepted
Abstract	This article describes diagnostic limitations and pitfalls of early computed tomographic and magnetic resonance imagings (CT and MRI) in patients with acute head injury. These imaging modalities provides us with anatomical and pathological information in the injured brain. A CT scan is considered essential for initial management of moderate to severe head injured patients, and MRI is useful for diagnosis of diffuse axonal injury (DAI). It is necessary to understand the limitations and potential pitfalls using CT and MRI to determine brain pathologies and the viewpoint of patients management in the acute stage. Head injuries are conveniently classified into three types: skull fractures, focal injuries and diffuse injuries. Diffuse injuries are associated with widespread disruption of neurologic function, and defined as head injuries, accompanied by consciousness disturbance without mass lesion on CT. They are divided into 3 subgroups: mild concussion, classic cerebral concussion and DAI. As the severity of injury increases, the amount of structural axonal damage increases, and therefore there is no absolute boundary between them. A major cause of axonal damage is shear strains that are generated by angular rotational acceleration/deceleration in a centripetal sequence of disruptive effect on brain function and structure (Ommaya-Gennarelli's hypothesis). Nevertheless, some observations suggest that mechanical components other than angular acceleration/deceleration may be significant in the genesis of diffuse injury. It is important to remember that there may be coexistence of two types of injuries (focal and diffuse), regardless of initial CT findings. A CT is essential for detecting lesions that need immediate neurosurgical interventions. Although plain skull x-ray films are useful for diagnoses of penetrating injuries, depressed fractures, radiopaque foreign bodies and child abuse, they are not recommended for use as a routine diagnostic tool in the early management of head injury. MRI is not currently indicated as an initial investigation for head-injured patients in the acute stage. MRI depict small hemorrhagic and non-hemorrhagic lesions (nonsurgical pathologies) not visible on CT, and is indispensable for diagnosis of diffuse injury (from concussion to DAI). T2* weighted images (T2*WI) are useful in demonstrating small intracerebral hemorrhages, while fluid-attenuated inversion recovery (FLAIR) sequences are more sensitive in showing subarachnoid hemorrhages than conventional MRI sequences. Diffusion-weighted images (DWI) improve the detection of non-hemorrhagic intracerebral lesions (axonal edema, ischemic lesion). FLAIR sequences are useful in depicting non-hemorrhagic lesions, too. Additional information of importance to the patient's prognosis can sometimes be detected using MRI.
Keywords	head injury, diffuse brain injury, acute stage, diagnostic imaging, pitfall