📚 Lecture Overview
This lecture explores the physiological consequences of spinal cord injuries, specifically focusing on complete transection and hemisection (Brown-Séquard syndrome). It details the stages of recovery following spinal cord trauma and explains the clinical presentation of syringomyelia, emphasizing the distinction between sensory and motor deficits based on the site of the lesion.
🎯 Key Concepts & Definitions
- Spinal Shock: A temporary loss of all spinal cord function and reflex activity below the level of injury immediately following trauma.
- Paraplegia: Paralysis affecting the lower half of the body, specifically both legs, usually caused by thoracic or lumbar spinal injuries.
- Quadriplegia: Paralysis of all four limbs and the torso, typically resulting from cervical spinal cord injuries.
- Dissociated Anesthesia: A condition where one sensation is lost (e.g., pain and temperature) while others (e.g., fine touch and proprioception) remain intact.
- Mass Reflex: A massive, uncoordinated emptying of the bladder and bowels, sweating, and flexion of all joints in response to a noxious stimulus below the lesion level.
📖 Main Content
1. Levels of Spinal Cord Transection
The site of the injury determines the clinical outcome and survival:
- Upper Cervical: Results in immediate death due to respiratory failure.
- Lower Cervical: Results in Quadriplegia; respiration is diaphragmatic but limited.
- Mid-Thoracic: Results in Paraplegia; respiration remains normal.
2. Stages Following Complete Cord Transection
If a patient survives the initial injury, they progress through several stages:
Stage I: Spinal Shock
- Duration: Temporary loss of function below the lesion.
- Symptoms: Total bilateral loss of motor and sensory function (pain, temp, touch, vibration).
- Reflexes: Temporary loss of all reflex activity (stretch and withdrawal reflexes).
- Autonomic: Hypotension and loss of vasomotor tone (especially if the lesion is at or above T6); loss of bladder and bowel control.
Stage II: Recovery of Reflex Activity
If the patient receives good medical care, reflexes return:
- Paraplegia in Flexion: The static component of the stretch reflex recovers more in flexors.
- Reflexes: Deep reflexes (like the knee jerk) become exaggerated; Babinski sign becomes positive.
- Autonomic Recovery: Micturition and defecation become automatic; the spinal sympathetic vasoconstrictor center becomes active.
- Specific Reflexes:
- Mass Reflex: Noxious stimuli cause sweating, pallor, and voiding.
- Coitus Reflex: Scratching the medial thigh causes erection and ejaculation.
- Paraplegia in Extension: Occurs in some cases with excellent care; characterized by increased tone in extensors, clonus, and the crossed extensor reflex.
Stage III: Failure of Recovery
- Occurs if complications like weight loss, bed sores, or toxemia develop, leading to death.
3. Hemisection of the Spinal Cord (Brown-Séquard Syndrome)
This occurs when only one side (half) of the spinal cord is damaged.
- Ipsilateral (Same Side) Effects:
- Paralysis of voluntary movements (UMN paralysis).
- Loss of Dorsal Column sensations (fine touch, vibration, position sense).
- Contralateral (Opposite Side) Effects:
- Loss of Pain and Temperature sensations (because the spinothalamic tract crosses at the spinal level).
4. Syringomyelia
A condition where fluid-filled cysts (syrinx) form within the central portion of the spinal cord.
- Mechanism: The cyst compresses the crossing spinothalamic fibers.
- Clinical Sign: Dissociated Anesthesia (bilateral loss of pain and temperature, but dorsal column sensations remain intact).
- Distribution: Usually follows a jacket distribution (lower cervical and upper thoracic regions).
- Progression: As the cavity grows, it can damage the Anterior Horn Cells (AHC), leading to muscle weakness and atrophy.
📊 Visual Learning
💡 Important Points to Remember
- Spinal Shock is the immediate reaction; reflex recovery happens later.
- T6 Level is the critical threshold for significant autonomic dysfunction.
- Babinski Sign is a classic indicator of UMN involvement during the recovery stage.
- Paraplegia in Flexion is more common than extension in complete transections.
- Mass Reflex involves sweating and bladder emptying triggered by skin stimuli.
- Brown-Séquard is the only syndrome where motor loss is on one side and pain loss is on the other.
- Syringomyelia causes a "jacket" pattern of sensory loss.
- In Syringomyelia, fine touch is usually preserved (Dissociated Anesthesia).
- Quadriplegia = Cervical; Paraplegia = Thoracic/Lumbar.
⚠️ Common Exam Questions
- The "Opposite Side" Trap: Examiners often ask which sensations are lost on the opposite side of a hemisection. Remember: Pain and Temperature are contralateral; Motor and Dorsal Column are ipsilateral.
- Syringomyelia Sparing: Questions often ask what is spared in syringomyelia. The answer is the Dorsal Column (fine touch/vibration).
- Reflex Status: Students often forget that reflexes are absent during spinal shock but exaggerated during the recovery stage.
- Respiratory Levels: Be careful with cervical injuries—upper cervical is fatal, while lower cervical allows diaphragmatic breathing.
📝 Quick Review Checklist
I can distinguish between the effects of upper and lower cervical injuries.
I understand the three stages following a complete spinal cord transection.
I can explain why pain is lost on the opposite side in Brown-Séquard syndrome.
I can define "Dissociated Anesthesia" in the context of Syringomyelia.
I know the components of the "Mass Reflex."
I can identify the clinical signs of the recovery stage (e.g., +ve Babinski, automatic bladder).