Mission
Neurology Networks tries to offer broad exposure to various topics that may be presented on the veterinary neurology board exam.
Neurosurgery 1
Q. Identify the structures encountered in the ventral slot approach.
A.
- Skin (incise from the caudal aspect of the laryngeal cartilages to the manubrium)
- SQ fat and fascial tissues
- Divide the sternocephalicus to the sternum
- Separate sternohyoideus mm from the laryngeal cartilages to the sternum, and bluntly dissect through the facial plane to the right of the trachea. Be careful to not damage the right caudal thyroid artery and caudal thyroid vein. You may have to cauterize the smaller branching vessels. The esophagus should be identified and retracted to the left. The recurrent laryngeal nerve will also be seen to the left along the trachea. The carotid sheath should be identified and retracted to the right.
- Identify the prominent ventral process of the first cervical vertebra and the large, ventrally directed transverse processes of C6. Use these to help localize the disc space of interest.
- Separate the longus colli muscles and separate the attachments from the ventral vertebral processes
- Longus capitis: muscles present just to the side of the longuscolli
- Intertransversarii intermedii cervicis: small muscles dorsolateral to longuscolli and ventral to transverse processes
- Drill through the bone centered over the disc space (position the drilling window with the caudal aspect starting at the annulus fibrosus (the disc slants cranially to ultimately be centered in the drilling window when the vertebral canal is encountered).
- Identify the outer cortical layer, inner medullary bone, then the inner cortical layer.
- Break through the inner cortical layer and dorsal annulus fibrosus to encounter the dorsal longitudinal ligament (DLL). Excise the DLL to see the herniated disc material and spinal cord.
- Be careful of the vertebral sinuses that lie on either side of the drilled window. The foramen and nerve root will be identifiable with a small probe.
- The spinal cord segments responsible for LMN control of the phrenic nerve (C5-7) are centered over C4-5, C5-6, and possible C6-7. UMN control runs through the more cranial segments from the brainstem. Injury to these areas can lead to hypoventilation or catastrophic respiratory failure.