No abstract

Heavily T2-weighted fluid-attenuated inversion recovery (FLAIR) sequences with inversion times of 2000-2500 ms and echo times of 130-200 ms were used to image the brain stem of a normal adult and five patients. These sequences produce high signal from many white matter tracts and display high lesion contrast. The corticospinal and parietopontine tracts, lateral and medial lemnisci, superior and inferior cerebellar peduncles, medial longitudinal fasciculi, thalamo-olivary tracts and the cuneate and gracile fasciculi gave high signal and were directly visualised. The oculomotor and trigeminal nerves were demonstrated within the brain stem. Lesions not seen with conventional T2-weighted spin echo sequences were seen with high contrast in patients with infarction, multiple sclerosis, sarcoidosis, shunt obstruction and metastatic tumour. The anatomical detail and high lesion contrast given by the FLAIR pulse sequence appear likely to be of value in diagnosis of disease in the brain stem.

No abstract

We present the characteristic imaging findings of hypoplasia of the internal carotid artery (ICA) in two cases, one accompanied by an intracranial aneurysm. Finding of a diffuse luminal narrowing of the ICA on MR angiography or digital subtraction angiography (DSA) could wrongly evoke severe acquired diseases such as dissection or atherosclerosis. Absence of associated wall thickening and flow disturbances on color Doppler sonography (CDS) should suggest carotid hypoplasia. Confirmation of the diagnosis is obtained by CT of the skull showing a small carotid canal. Non-invasive procedures are sufficient to differentiate this rare congenital anomaly from acquired string signs.

The authors describe an unusual case of a complex traumatic fracture-dissociation injury of the craniovertebral junction, which the patient survived with no neurological damage. This case featured the rare combination of an avulsion of both the right occipital condyle and clivus and a fracture of the left lateral mass of the atlas. Because of the craniocervical ligament injury and the slight anterior occipitoatlantal dislocation, the lesion was considered to be unstable and was treated successfully with a cervical collar. The authors emphasize that thin-slice computerized tomography scanning with multiplanar reconstructions is essential to visualize these fractures, whereas magnetic resonance imaging is useful to assess soft tissues.