Sensory Exam
Anatomy of the Sensory System
- You will get the anatomy in detail from Dr Scott so I will review it only to highlight clinically relevant points
- The 2 main sensory pathways, the posterior columns/medial lemnicus system (PC/ML)and the anterolateral system (ALS), each contain 3 neurons
- The ALS crosses over in the spinal cord whereas the PC/ML crosses over in the medulla
- This means that a patient with a spinal cord lesion could have loss of pain and temperature on one side and loss of position sense and vibration on the other side
Anterolateral System
- The 1st order neurons enter the spinal cord and may ascend in Lissauer’s tract (see red square) for 2-3 segments before synapsing in the dorsal horn or the second order neurons may take 2-3 segments as they move in the anterior commissure (see green square)before crossing over into the white matter of the anterolateral pathway on the contralateral side
Reflection
What is the clinical importance of this fact?
Reflection
If the first order neurons of the anterolateral system are impaired, what other system would you want to ask the patient about?