Sagittal T1-weighted sequence cervical and upper thoracic spine.Normal CSF is of low signal intensity and this is seen within the spinal canal at the cervical spine level. The spinal subarachnoid haemorrhage is demonstrated as abnormal high signal intensity posterior to the cord at the level of the T1 vertebral body (red arrow), this extends caudally all the way down the spinal canal and is seen within the distal thoracic and lumbar spine. CSF: cerebrospinal fluid.