Structural Neuroanatomy Flashcards
How many spinal nerves? Which levels?
31 total. 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal.
Which SC levels have sympathetic neurons?
T1-L2
Which SC levels have parasympathetic neurons?
Brainstem / cervical and S2-4
Dermatomes for nipples, umbilicus, and perineum
Nipples at T4
Umbilicus at T10
Perineum at S3
General characteristics seen in myopathies.
Symmetric proximal muscle weakness
Waddling gait
Caused by myopathy. Pelvis falls on the side of the striding leg due to hip muscle weakness.
What part of body do myopathies usually not affect?
Face / orbits
What parts of body do NMJ-opathies usually affect?
Eyes, face, pharynx, and larynx
Most common mononeuropathies in order
Median, ulnar, radial, lateral femoral cutaneous, and common peroneal
Most comon radiculopathies in order
L5, S1, C7, C6
General characteristics seen w/ polyneuropathies.
Symmetric distal abnormalities. Sensory and motor, but sensory predominate. Stockings & gloves. Lose proximal reflexes early on. May also lose position sense –> ataxic gait (wide stance). Slapping gait and steppage gait are also possible. Autonomic dysfunction may occur in severe cases, w/ orthostatic hypotension being the first symptom.
Cause and sxs of carpal tunnel syndrome
Median nerve. Most common mononeuropathy.
Sensory and motor. Thumb through half of ring finger on palm side. Finger tips on back as well. Palm is spared due to branch that passes outside the tunnel. Median controls thenar muscles, which control opposition, abduction, and flexion of the thumb. Abduction and flexion may be spared though due to redundant muscles in the forearm. May get atrophy, which is a lower motor neuron sign.
Ulnar neuropathy
Somatosensory for pinky and rest of ring finger; front and back. Ulnar nerve controls all other intrinsic hand muscles (other than thenar muscles). Ab / adduction of fingers, extension of ring / little finger, pinky opposition. Arm muscles that control flexion of ring / little finger and wrist flexion may be effected.
Radial neuropathy cause and sxs
Radial nerve wraps around ulnar / spiral groove on posterior part of humerus. May be compressed → problems in wrist / finger extension. “Wrist drop”. “Weakness in grip”. Other affected muscles include thumb abduction, hand supination, and elbow flexion. Brachioradialis reflex may be diminished.
Last part of somatosensation in back of hand on thumb side through half of ring finger (but proximal fingers, not distal, which is median nerve)
Lateral femora cutaneous neuropathy
Compression at inguinal ligament (may occur w/ wearing tight pants [putting on weight]) – somatosensation of lateral thigh. Numbness, pain, or parasthesias may be present.
Common peroneal neuropathy at the knee
Common peroneal / fibular nerve wraps around femoral head. Somatosensation to lateral lower leg and top / medial side of foot. Innervates muscles for foot dorsiflexion, toe extension, and eversion of foot. Problem called foot drop.
5th lumbar radiculopathy
Most common radiculopathy.
•Somatosensation: Lateral leg and top / medial side of foot. Same as common peroneal nerve in lower leg, but peroneal does not deal with thigh at all.
•Weakness w/ hip abduction, knee flexion, foot dorsiflexion, foot eversion, foot inversion, and toe extension. Foot inversion weakness is only feature distinguishing from common peroneal.
•L5 reflexes are normal.
Radicular pain
Shooting down a limb. Called sciatica if it occurs in the leg.
1st sacral radiculopathy
Lateral side of foot. Lose ankle jerk reflex. Others obvious.
7th cervical radiculopathy
- Somatosensory: Posterior proximal / distal arm, posterior hand, and anterior / posterior middle finger.
- Motor: Weakness of middle finger, hand pronation, wrist flexion / extension, finger extension and elbow extension. Lose triceps reflex
6th cervical radiculopathy
- Problems w/ elbow flexion, hand supination, wrist extension.
- Lose biceps and brachioradialis reflexes
Funiculi
white matter columns in spinal cord
Where does viscerosensory info ascend?
Ascends near spinothalamic tract. Unconscious position sense ascends mainly ipsi in spinocerebellar tract.
From where do spinal arteries originate?
Originate from the vertebral arteries in the neck, but are mainly supplied by the cervical arteries and segmental arteries from the aorta.
Medial cerebellum
Medial cerebellum consists of midline vermis, adjacent medial cerebellar hemispheres (paravermis), and flocculonodular lobe inferiorly. Vermis and paravermis project to interposed and fastigial nuclei in cerebellum, which project to brainstem. Flocculonodular lobe projects to vestibular nuclei in brainstem.
Medical cerebellar syndrome
- Medial cerebellum controls gait, torso, and neck.
- Main problem is gait ataxia, which has a wide base and is unsteady.
- Truncal ataxia – px unable to sit unassisted
- Vertigo possibly due to interconnections w/ vestibular system.
- Slurred speech (dysarthria)
- Nystagmus
What is isolated ataxia caused by?
Dysfunction in cerebellum
Lateral cerebellar syndrome
- Lateral cerebellum controls ipsi limb movement.
- Vertigo, slurred speech, but no gait ataxia. Instead get limb ataxi
- Dysmetria – limb misses target
- Intention tremor – occurs when approaching target
- Ipsilateral abnormalities due to double cross pathway
Multifactorial abnormal gait
AKA ?
AKA cautious / hesitant gait
Hesitant, short-striding, unsteady gait on normal base. Due to dysfunction of multiple sensory systems
Where does each CN attach to brainstem?
CN IX, X, and XII connect to medulla. CN VI, VII, and VIII connect to pontomedullary junction. CN V is attached to pons. CN III and IV attach to midbrain.
Accessory nucleus
Consists of LMNs in dorsal horn of C1-5. Axons ascend just lateral to cervical SC. Nerve enters skull and quickly exits again
Hypoglossal neuropathy
Nerve runs inferior to tongue. Damage → atrophy / fasciculations of the tongue. Tongue deviates to ipsi side. Genioglossus normally protrudes the tongue anteriorly.
Vagus neuropathy
Problems in larynx / palate. May have dysarthria, dysphagia, dysphonia, nasal regurgitation, ipsi palate elevation weakness, ipsi efferent pharyngeal reflex dysfucntion.
Not many autonomic problems due to redundancy.
Viscerosensation travels to solitary nucleus.
Where are LMNs for palate / pharynx / larynx found?
ambiguus nucleus in medulla
Where are preganglionic parasympathetic cell bodies for viscera found?
Posterior vagus nucelus in medulla.
Glossopharyngeal neuropathy
Sensory loss of pharynx and posterior tongue to trigeminal nucleus. Ipsi afferent dysfunction of gag reflex. Taste from posterior tongue to solitary nucleus. Preganglionic parasympathetics from inferior salivary nucleus.