Lab 9: Spinal Cord Reflexes
Learning Objectives – Neurological examination
- Know how to perform standard postural reactions:
- Proprioceptive placing
- Hopping.
- Perform the following spinal reflexes
- Patellar
- Withdrawal reflex (thoracic and pelvic limb)
- Perineal reflex
- Cutaneous trunci reflex
- Be able to explain the difference between a reflex and a response.
Learning Objectives – Anatomical knowledge associated with the neurological examination
- Understand the components of the nervous system involved in postural reaction testing.
- Name the spinal cord segments and efferent nerve(s) involved in the following spinal reflexes:
- Patellar
- Withdrawal reflex (thoracic and pelvic limb)
- Perineal reflex
- Know the pathway for the cutaneous trunci reflex (afferent and efferent arms) and be able to
explain why the level of cutaneous sensation lies caudal to the spinal cord segment being
tested.
Learning Objectives – Neurolocalization section
- Localization of Spinal Cord Lesions – use gait and spinal reflexes to localize to
- C1-5
- C6-T2
- T3-L3
- L4-S3
- Understand how to localize a lesion to the peripheral nervous system
In Preparation for the Spinal Lab
What we will do:
Hands on lab
- Learn how to test postural reactions
- Hopping
- Proprioceptive placing
- Learn how to test spinal reflexes
- Patella
- Withdrawals
- Perineal
- Cutaneous trunci
- Answer questions about the anatomy behind these functions
Neurolocalization exercises
- Review UMN and LMN paresis
- Discuss how to localize to C1-5, C6-T2, T3-L3, L4-S3 and generalized LMN(neuromuscular)
- Practice!
For the hands on lab
When evaluating gait:
- Looking for number of legs affected, and whether they have:
- Lameness
- Ataxia
- Paresis
- Classification of paresis
- ‘Plegia – complete loss of voluntary motor function
- ‘Paresis – partial loss of voluntary motor function
- Mono – one limb affected
- Para – both hind limbs affected
- Hemi – ipsilateral thoracic and pelvic limb affected
- Tetra – all 4 limbs affected
- Classification of ataxia
- Proprioceptive
- Vestibular
- Cerebellar
When evaluating reflexes (relevant in patients with paresis)
- Withdrawal reflex in the thoracic and pelvic limb
- Extend the limb, pinch the toe and pull gently against as they withdraw, looking for flexion of all the joints.
- Thoracic limb – assesses C6-T2 spinal cord segments
| Joint | Nerve | Spinal cord segment |
| Elbow flexion | Musculocutaneous | C6-8 |
| Carpal flexion | Median/Ulnar | C8-T2 |
| Digital flexion |
- Pelvic limb – assesses L4-S2, but because we have the patellar reflex to assess L4 – 6 we focus particularly on the hock joint and use this to assess L6 – S2 spinal cord segments and the sciatic nerve and its branches.
| Joint | Nerve | Spinal cord segment |
| Hip flexion | Femoral | L4-6 |
| Stifle flexion | Sciatic | L(6)7-S2 |
| Tarsal flexion | Common Fibular (Peroneal) | L(6)7-S2 |
| Digital flexion | Tibial | L(6)7-S2 |
- Patellar reflex in the pelvic limb: assesses femoral nerve and spinal cord
segments L4-6- When lying in lateral recumbency, tap the straight patellar ligament and look for a sharp, clean flick of the foot due to contraction of the quads.
- Perineal reflex – assesses the pudendal nerve and spinal cord segments S1-3
- Pinch the skin in the perineal region and look for contraction of the anus, the tail might also move ventrally.
- When you take a temperature you can see this reflex.
- If unsure of anal tone, you can do a rectal exam
- Cutaneous trunci reflex
- Starting at the level of the wings of the ilium, pinch the skin of the back 2 – 4 cm to either side of the midline and look for the muscle twitch over the trunk – continue moving forwards until a twitch is seen and stop there.