Spinal Cord Flashcards
(19 cards)
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
