Spinal Cord Flashcards
What kind of fibers and what type of sensation carry the medial division of the dorsal root entering to the dorsal horn of the spinal cord?
- Ia (muscle spindle or muscle stretch receptor) Ib fibers (Golgi tendinosus organ) ▶️ propioception (participation in reflex)
- II, A-beta ▶️ touch
What pathways may produce a muscle contraction using the upper and lower motoneuron?
- voluntarily contraction: UMN ▶️ LMN ▶️ skeletal muscle
- reflex: fiber IA (muscle sensory neuron [afferent] from muscle spindle) ▶️ LMN ▶️ skeletal muscle
- UMN control over reflexes - inhibitory effect
- both alpha and gamma motoneurons (LMN) participate in reflexes
Functions of the muscle spindle (intrafusal muscle fibers)
- sensory receptor in skeletal muscle stretch reflexes
- monitor the length and the rate of change in length of extrafusal fibers ▶️ connected in parallel with it
Function of the Golgi tendon organs, what type of fibers are the afferents that innervates them?
- inverse muscle stretch reflex: monitor muscle tension
- Ib fibers
Role of gamma motoneurons in tension and reflexes
- if they are (+) ▶️ contraction of intrafusal muscle fibers to contract at muscle spindle ▶️ (+) Alfa motoneuron ▶️ ⬆️ muscular tone
In case of UMN lesion, when do you get a decorticate or decerebrate rigidity? Why does it occur?
- decorticate rigidity (flexion arm, extension leg) ▶️ lesion above midbrain
- decerebrate rigidity (extension arm and leg) ▶️ lesion below midbrain
- no inhibition on muscle stretch reflexes by UMN on LMN
What is the Babinski sign and for what is useful? Why does it occur?
- extension of the great toe and fanning of other toes (reversal of cutaneous reflex) with cutaneous stimulus (stroking lateral surface of foot - normally flexor response)
- corticospinal lesion - UMN lesion
What axons of the 3 neurons participating in sensory system pathways at the spinal cord or brain stem crosses the midline?
- axons of the second-order neuron in CNS
Where is the second neuron in the dorsal column-medial lemniscal system?
Medulla (lower part) - nucleus gracilis and cuneatus
*fibers from these nuclei crosses the midline - ascend as medial lemniscus
Mention 3 signs to evaluate lesions at dorsal columns
- astereognosis
- vibratory sense: tuning fork, loss.
- Romberg sign: positive
How is the presentation when a lesion occur in anterolateral (spinothalmic tract) system? What signs or symptoms can you find?
- contralateral and 1 or 2 segments below the lesion, everything below that level
- “anesthesia”: loss pain and temperature
What disease could cause a lesion in spinocerebellar tracts?
- friedreich ataxia ▶️ degeneration of spinocerebellar pathways
- ataxia of gait most common initial symptom
When do you have spastic bladder and how do you identify it?
Lesion of spinal cord above sacral spinal cord levels
- urge incontinence
- loss inhibition parasympathetic fibers ▶️ detrusor muscle respond to minimum amount of stretch during filling stage
When do you have atonic bladder and how do you identify it?
Lesion to the sacral spinal cord segments
- continuous dribble of urine
- loss parasympathetic innervation ▶️ loss contraction of detrusor ▶️ full bladder
What type of spinal cord lesion results as a late-stage of syphilis? Symptoms.
- tabes dorsalis (dorsal column, and dorsal roots degeneration)
- paresthesias, pain, polyuria (incontinence), Romberg sign, “high-step stride”, argyll Robertson pupils, ⬇️ reflex, ataxia, astereognosis, impaired vibration
Clinical presentation of amyotrophic lateral sclerosis
- Progressive spinal muscular atrophy (ventral horn)
- Bilateral flaccid paralysis in upper limbs - Common in cervical enlargement (often begins here) ▶️ progress up or down
- Bilateral spastic weakness of the lower limbs - Primary lateral sclerosis (corticospinal tract)
- Increased tone and reflexes
Clinical presentation of occlusion of the anterior spinal artery
- Loss bilateral temperature and pain below the level of lesion
- Bilateral spastic paresis below the level of lesion
- Spastic bladder
- common at thoracic levels
Clinical presentation of subacute combined degeneration
- Bilateral spastic paresis below the lesion site
- Bilateral alteration of touch, vibration, pressure sensation below the lesion site (other signs of dorsal column involvement may be present)
- upper thoracic and lower cervical cord common
Clinical presentation of syringomielia
Progressive
- Early: bilateral loss of pain and temperature sensation in the hands and forearms
- Then: bilateral flaccid paralysis of upper limbs
- Late: Horner syndrome
- usually at cervical level
