If a bronchus is torn all the way around, the lung may collapse outward toward the chest wall (rather than inward, as it usually does in pneumothorax) because it loses the attachment to the bronchus which normally holds it toward the center. In a person lying face-up, the lung collapses toward the diaphragm and the back. This sign, described in 1969, is called fallen lung sign and is pathognomonic of TBI (that is, it is diagnostic for TBI because it does not occur in other conditions); however it occurs only rarely. In as many as one in five cases, people with blunt trauma and TBI have no signs of the injury on chest X-ray. CT scanning detects over 90% of TBI resulting from blunt trauma, but neither X-ray nor CT are a replacement for bronchoscopy.At least 30% of TBI are not discovered at first; this number may be as high as 50%. In about 10% of cases, TBI has no specific signs either clinically or on chest radiography, and its detection may be further complicated by concurrent injuries, since TBI tends to occur after high-energy accidents. Weeks or months may go by before the injury is diagnosed, even though the injury is better known than it was in the past. Classification
Lesions can be transverse, occurring between the rings of the trachea, longitudinal or spiral. They may occur along the membranous part of the trachea, the main bronchi, or both.
Alkaloids present in plants of the genera Brugmansia and Datura, such as scopolamine, may also induce anisocoria. Migraines

Diagnosis
Causes of anisocoria range from benign (normal) to life-threatening conditions. Clinically, it is important to establish whether anisocoria is more apparent in dim or bright light to clarify if the larger pupil or smaller pupil is the abnormal one. Anisocoria which is worsened (greater asymmetry between the pupils) in the dark suggests the small pupil (which should dilate in dark conditions) is the abnormal pupil and suggests Horners syndrome or mechanical anisocoria. In Horners syndrome sympathetic nerve fibers have a defect, therefore the pupil of the involved eye will not dilate in darkness. If the smaller pupil dilates in response to instillation of apraclonidine eye drops, this suggests Horners syndrome is present. Anisocoria which is greater in bright light suggests the larger pupil (which should constrict in bright conditions) is the abnormal pupil. This may suggest Adie tonic pupil, pharmacologic dilation, oculomotor nerve palsy, or damaged iris.A relative afferent pupillary defect (RAPD) also known as a Marcus Gunn pupil does not cause anisocoria. Some of the causes of anisocoria are 
life-threatening, including Horners syndrome (which may be due to carotid artery dissection) and oculomotor nerve palsy (due to a brain aneurysm, uncal herniation, or head trauma). If the examiner is unsure whether the abnormal pupil is the constricted or dilated one, and if a one-sided drooping of the eyelid is present then the abnormally sized pupil can be presumed to be the one on the side of the ptosis.