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.
Pharyngeal reflex
Unilateral afferent carried by glossopharyngeal nerve and bilateral efferent carried by vagus nerve for gag reflex.
Which nerve controls stapedius?
CN VII
Facial nucleus / nerve
Stapedius
Taste sense from anterior tongue travels in facial nerve to solitary nucleus. Preganglionic parasympathetic neurons of superior salivary nucleus in pons travel in this nerve to innervate lacrimal gland and salivary glands. May have abnormal efferent corneal reflex.
Where are neurons for stretch of muscles of mastication
Mesencephalic trigeminal nucleus, which projects to motor trigeminal nucleus for stretch reflex.
Which nerve controls tensor tympani?
CN V
Trochlear neuropathy
Superior oblique muscle.
Intorsion weakness causes extorsion causing diplopia. To fix this, people turn their head away. Normal eye intorts to line up.
Orientation of superior / inferior recti
45 degree angle w/ anterior being lateral.
Pathway for sympathetics to eye vs to sweat glands.
Sympathetics to orbit travel along internal carotid artery. Sympathetics to sweat glands of face travel along external carotid artery.
Tegmentum vs tectum
What is found in the tectum?
Tegmentum is posterior part of brainstem. Tectum is even further posterior, only found in the midbrain.
Tectum contains inferior / superior colliculus.
What does the reticular formation do?
Controls circulation, respiration, and digestion
Anterior circulation
Anterior circulation – arteries arising from intracranial parts of internal carotid arteries, which gives off ophthalmic artery (which gives off retinal artery), anterior choroidal artery to deep cerebral hemisphere, and then divides into ACA and MCA. Anterior communicating artery connects right / left ACA.
Posterior circulation
All arteries arising from intracranial parts of vertebral arteries
What does MCA supply?
MCA supplies lateral frontal, parietal, temporal, and insular lobes, BG, and internal capsule. May get contra homonymous hemianopsia due to optic radiation.
What does PCA supply?
PCA supplies medial temporal / occipital lobes and thalamus. May get contra homonymous hemianopsia.
Where does PICA branch off?
What does it supply?
From vertebral arteries
Supplies medulla and lower cerebellum.
Where does AICA branch off?
What does it supply?
Branches off inferior basilar artery.
Supplies middle cerebellum.
Where does SCA branch off?
What does it supply?
SCA arises from superior basilar artery
Supplies superior cerebellum.
Medial medullary syndrome
Mainly supplied by small arteries from vertebral and anterior spinal arteries. From anterior to posterior: pyramid, medial lemniscus (contra fine touch), trigeminothalamic tract (pain, temp, gross touch from contra face via spinal trigeminal nucleus), and hypoglossal nucleus (axons exit lateral to pyramid).
Lateral medullary syndrome
AKA Wallenberg syndrome) – Supplied by PICA. No UMN’s so no weakness. Descending sympathetics to orbit (Horner’s Syndrome). Posterior vagus nucleus. Solitary nucleus for taste from anterior tongue (via facial nerve), posterior tongue (via glosspharyngeal nerve), and pharynx (vagus nerve). Solitary nucleus also receives viscerosensory info from viscera via SC, CN IX / X. Vestibulocochlear nucleus and inferior olive (connected to cerebellum). Inferior salivary nucleus via CN IX. Ambiguus nucleus for LMNs to palate / pharynx / larynx / gag reflex via vagus nerve. Spinothalamic tract (contra pain, temp, gross touch), vestibular nuclei (vertigo), inferior cerebellar peduncle w/ spinocerebellar tracts, spinotrigeminal nucleus (pain, temp, gross touch, and afferent gag reflex for ipsi face; enters ipsi pons, descends to ipsi spinotrigeminal nucleus, then ascends to ipsi thalamus; split brainstem syndrome: contralteral body, ipsi face)
Medial pontine syndrome
Mainly supplied by basilar artery.
•Basis pontis w/ corticospinal / corticobulbar / corticopontine tracts.
•Medial lemniscus and trigeminothalamic tract (contra face pain, temp, gross touch) are found in inferior anterior tegmentum and move laterally as they ascend.
•Superior pons has axons from contra main trigeminal nucleus (contra face position, vibration, fine touch).
•MLF and abducens nucleus found in posterior tegmentum. MLF disruption → internuclear ophthalmoparesis (on left gaze, left eye moves left but right eye cannot). Convergence is spared due to convergence center and oculomotor nuclei in midbrain being intact. Facial nucleus wraps around abducens nucleus → ipsi facial weakness.
Lateral pontine syndrome
Supplied by basilar artery, AICA, and SCA. Facial nucleus and vestibulochoclear nucleus are in inferior tegmentum. Spinothalamic tracts (pain, temp, gross touch of contra body), trigeminal nucleus (ipsi sensation to face and muscles of mastication). Corneal reflex carried via trigeminal nerve (afferent) to facial nuclei (efferent). Lateral lemniscus (auditory). Hyperacusis due to stapedius (VII) or tensor tympani (V). Descending sympathetics to eye (Horner’s). Axons from contra basal pontine nuclei to middle cerebellar peduncle.
Locked-in Syndrome
Bilateral lesion of basis pontis due to basilar artery. Can’t move / speak. Corticobulbar and corticopontine tracts. Fully conscious and fully sensitive. Intact vertical gaze centers and oculomotor nuclei allow for vertical gaze and eyelid closure.
Medial midbrain syndrome
Supplied by PCA.
•Loss of corticopontine / corticospinal / corticobulbar tracts, SN, red nucleus, CN III nucleus / nerve (levator palpebrae), Edinger-Westphal nucleus (preganglionic parasympathetics to iris constrictor & ciliar muscle), CN IV (axons decussate before exiting brainstem posteriorly), vertical gaze / convergence centers.
•Dentato-thalamic tract from cerebellum to thalamus → ataxia on one or both sides.
•Tectum: pretectum (sight). Inferior colliculus (sound) and superior colliculi (moves head / eyes toward stimuli, blinking, ducking).
•Sensory stuff is preserved due to being more lateral.
Lateral midbrain syndrome
Supplied by PCA. Corticospinal / corticobulbar / corticopontine / spinothalamic / trigeminothalamic tracts, medial / lateral lemnisci, SN, descending sympathetics to orbit (Horner’s)
CSF pathway
Choroid plexus –> lateral ventricles –> interventricular foramen –> 3rd ventricle –> cerebral aqueduct –> 4th ventricle –> central canal of SC
Anterior / posterior commisures
smaller bundles of axons that connect the 2 hemispheres
Where is caudate?
Lateral to lateral ventricle. Head is medial to anterior limb of internal capsule.
Lentiform nucleus
Putamen + globus pallidus. Found lateral to internal capsule.
Striatum
Caudate + putamen
Parkinsonian gait
stooped, slow, shuffling, diminished arm swing
Where is thalamus?
lateral to lateral ventricle and medial to posterior limb of internal capsule
Amaurosis fugax
Transient monocular visual loss due to dysfunction of retinal artery
Dysfunction of medial vs lateral occipital cortex
Unilateral dysfunction of medial cortex → contra homonymous hemianopsia. Lateral dysfunction → visual agnosia from involvement of visual association cortex
Where are the auditory and olfactory cortices?
Temporal lobe.
Auditory (superior), olfactory (anterior / medial)
Paraphasia
Word error. May have similar sound, meaning, or neither.
Lateral temporal syndrome
Don’t get hearing loss unless there is bilateral auditory cortex damage. Contra superior homonymous quadrantanopsia due to lesion of inferior optic radiation.
Lateral parietal syndrome on nondominant side
Agraphesthesia, astereognosis, hemineglect.
Also get contra inferior homonymous quadrantanopsia due to superior optic radiation.
Lesion to insular cortex
Insular cortex involves gustation, vestibular, and viscerosensory. Lesions usually do not cause dysfunction due to bilateral redundancy. Lesion on left side may cause aphasia due to arcuate fasciculus.
What is included in a mental status exam?
Arousal (responsiveness to stimuli), orientation (to person, place, time, or situation), attention, language, memory, fund of knowledge (facts or current events), and executive function
Extinction
Observation of hemineglect only during bilateral stimuli
Where does Broca’s area project?
Primary motor cortex.
From where does Wernicke’s Area receive input?
Primary auditory / visual cortex.
Anomia
Abnormal naming
Broca’s aphasia
Includes impaired repetition
Transcortical motor aphasia
Normal repetition. Caused by dysfunction around, but not in Broca’s area or arcuate fasciculus.
Wernicke’s aphasia
Includes impaired repetition
Transcortical sensory aphasia
Normal repetition. Caused by dysfunction around, but not in Wernicke’s area.
Conduction aphasia
Isolated deficit of repetition due to damage in arcuate fasciculus
Prosody
Emotional content of speech / inflection. Found in nondominant cortex in areas analogous to Broca and Wernicke.
What structures aid in forming / storing memory of learned movements?
Cerebellum and BG
Abulia
Deficit of motivation
What parts of brain make up the reticular activating system?
Reticular formation and parts of thalamus that project glutamate to cortex
What is required for arousal / attention?
Require Ach from basalis / septal nuclei in inferior frontal lobe and histamine from hypothalamus
Circadian rhythm entrapment
Involves retinal ganglion cells that synapse in hypothalamus, which regulate release of melatonin from pineal gland, found posterior to thalamus.
Vegetative state
Wakefulness w/o awareness lasting more than 1 month
Minimally conscious state
Observable, but minimal purposeful behaviors or responses to stimuli
