MOD3-Neuro Flashcards
Cranial Nerves
– 12 pairs emerging from (mainly brainstem) within the skull
– Motor, sensory or specialized functions
– Symptoms specific to area and function of nerve
– CN deficits: nerve or brain lesions
Spinal Cord
– Extends from medulla (brainstem) to L1-2
– Becomes cauda equina below L2
– Contains motor and sensory nerve pathways
– Mediates reflex activity of deep tendon reflexes
Spinal nerves
– Connect spinal cord with muscles and peripheral sensory receptors
– Nerve roots exit vertebral (spinal) column through neural foramina
– Each spinal nerve has an anterior (motor) and a posterior (sensory) root
– 31 pairs of spinal nerves attach to the spinal cord – 8 cervical, 12 thoracic, 5 lumbar and 5 sacral, 1 coccygeal
Neural Pathways
Three Main “Super-Highways” of brain and spinal cord
– Corticospinal Tract Motor
– Spinothalamic Tract-Sensory
– Posterior Column-Sensory
Primarily located in brainstem and spinal cord
Corticospinal tract: motor pathway
– White matter connection between cerebral cortex and lower medulla into the anterior horn cells of the spinal cord
– Decussates- nerve crossing over spinal cord.
– Upper motor neuron
– Lesion on C7- ipsilateral weakness
– Lesion in brain- crosses thus opposite side from brain lesion
– Responsible for muscle tone and skilled, voluntary movements
Locating source of motor deficits
– If corticospinal tract is damaged, motor function is affected below the level of injury
– If neurons are damaged above crossover tracts in medulla, motor impairment is on opposite (contralateral)
– If lesion is in spinal cord motor impairment is on the same(ipsilateral)
Upper motor neuron problem (CNS to cord); IE: stroke (Peripheral just going no control)
– Affected extremity is spastic
– Increased muscular tone
– Increased reflexes
– Positive Babinski
Lower motor neuron problem (anterior horn to peripheral nerve)IE: herniated disc. NO signal.
– Affected extremity is flaccid
– Decreased muscular tone
– Decreased/absent reflexes
– Atrophy and fasciculations
Spinothalamic tract(sensory tract)
– AFFERENT
Transmits pain, temperature, and crude touch sensation from spinal cord to thalamus
– Fibers cross to contralateral side at the posterior horn SPINAL CORD and travel up
– Lesions IN CNS cause contralateral anesthesia
– Loss of pain- Sharp/dull – evaluating pain
– Loss of temperature
– Unmyelinated- fast
– Same level of cross over of spinal cord
–
Posterior column(sensory tract)
– Transmit fine touch, pressure, vibration, and proprioception from posterior column to thalamus
– Fibers cross to contralateral side in the medulla
Peripheral neuro: the motor exam
Motor exam (corticospinal tract) – combined with musculoskeletal system
– Myotomes (peripheral nerves to muscles)
– Corticospinal tracts
– Body position at movement and rest
– Involuntary movements: tremors, tics, fasciculation
– Muscle bulk: atrophy LMN
– Muscle tone: rigidity to passive ROM, spasticity, cog wheeling
– Muscle strength: resistive ROM. Compare for symmetry, OBJ
Peripheral neuro: the sensory exam
– Dermatomes (spinal nerves)
– Deep tendon reflexes (spinal reflexes) (use reinforcement somewhere else, strenthers, hand clasp, clinch jow, or squeeze knees. Finger on tendon, then wider edge. If no finger, then smaller end. Look for muscle twitch. Take to length on tendon.
– Sensory modalities (spinothalamic tract, posterior columns)
Cerebellum exam-balance & coordination
Myotomes UPPER- test in middle ROM, break test
– Elbow flexion-C5, C6;
– Elbow and wrist extension- C6, C7, C8;
– Grip-C7, C8, T1;
– Finger abduction(ulnar nerve): C8, T1.
– Opposition of thumb: C8, T1(median nerve)
Myotomes LOWER test in middle ROM, break test
– Flex at hip - L2,L3, L4; Extend hip- S1 – ADDuct hip - L2, L3, L4; – ABD hip-L4, L5, S1; – Extend knee - L2, L3, L4; – Flex knee - L4, L5, S1 – Dorsiflex-L4, L5; – Plantarflex-S1
Sensory receptors found in:
– Skin – Mucous membranes – Muscles, tendons – Viscera GSA
Sensory Function
Skin receptors for different kinds of sensation send afferent impulses to spinal cord via peripheral and spinal nerves
– Impulses travel via spinothalamic tract or posterior columns to thalamus
– Impulses then travel to cortex for fine interpretation
Tips for sensory testing
– Compare for symmetry
– For pain, temperature and touch sensation compare distal to proximal areas
– If detect an area of sensory loss map out its boundaries
– Ask yourself questions of central vs peripheral. Bilateral vs unilateral. Pattern of sensory loss suggest dermatomal distribution, polyneuropathy or spinal cord syndrome
– MD- marker will help determine what nerve and where
Dermatomes
– A dermatome is a band of skin innervated by the sensory root of a single spinal nerve
– abnormal sensation w/in dermatome identifies location of injury
– Can be variable
Nerve root or cutaneous(peripheral nerve)?
– Important to due sharp or dull (control)-to determine peripheral or cutaneous.
– Cutaneous- mixed spinal nerves large patches, many
– Dermatomes-linear lines
Spinal Reflexes: Deep Tendon Response
– Involuntary reflex arc between afferent and efferent nerves in spinal cord
Sensory impulse directly stimulates motor fiber
– Reflex – involuntary stereotypical response
– Hyperactive- UMN
Stereotypical – oversimplified
– Weakness and sensation changes can be tricky.
– *Reflexes are the most important test when determining a central vs peripheral process
– Damage to the corresponding spinal nerve, damaged peripheral nerves or disease of the muscle can all cause a LMN(peripheral nerve issue)
– Each reflex involves specific spinal segment
– abnormal finding will be helpful in location of problem
Deep Tendon Reflexes
– Specific to nerve root(dermatome) Stretch the muscle
– Increased or decreased?
– hyperactive reflex think UMN (CNS).
– Absent/diminished think LMN (PNS)
Grading scale-DTR; Look for muscle contraction, no necessary the movement
– 0 = no response; always abnormal
– 1+ = a slight but definitely present response; may or may not be normal
– 2+ = normal
– 3+ = a very brisk response; may or may not be normal
– 4+ = a tap elicits a repeating reflex (clonus); always abnormal
– Clonus-fasciculations with DTR. MRI STAT
Reflexes tested-Consider reinforcement if necessary to increase reflex activity; jaw clinch, knee squeeze, or hand clasp
Biceps – C5, C6 Triceps – C6, C7 Brachioradialis – C5, C6 Patella – L2, L3, L4 Achilles – S1 Abdominal – T8-12- Abdominal reflex should show contraction of abdominal wall muscles and deviation of the umbilicus toward the stimuli Plantar – L5, S1