Give me different parts of brain and spinal cord and their functions devided into motor sensory and other if present for general medicine cns case in clinical posting
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I've used up my database query budget. I have excellent knowledge of this topic from authoritative neurology and neuroanatomy sources. Let me now compose a thorough, well-organized answer based on standard neuroanatomy and clinical neurology texts (Adams & Victor, Gray's Anatomy, Guyton & Hall, Localization in Clinical Neurology).
CNS Structure & Function - Clinical Neurology Reference
How to Use This in Clinical Posting
When examining a CNS case, localize the lesion by matching deficits to the region below. Deficits are grouped as Motor, Sensory, and Other (autonomic/cognitive/reflex/special functions).
1. CEREBRAL CORTEX
Frontal Lobe
| Domain | Area | Function | Deficit if Damaged |
|---|---|---|---|
| Motor | Primary motor cortex (M1, precentral gyrus) | Voluntary movement of contralateral body | Contralateral UMN hemiplegia/hemiparesis |
| Motor | Premotor cortex | Planning and coordination of movement | Apraxia (inability to perform learned movements) |
| Motor | Broca's area (dominant hemisphere, BA 44/45) | Motor speech production | Expressive (Broca's) aphasia - non-fluent speech |
| Motor | Frontal eye field (BA 8) | Voluntary saccades - eyes move away from lesion | Eyes deviate TOWARD the side of an acute destructive lesion |
| Other | Prefrontal cortex | Executive function, judgment, personality, working memory | Disinhibition, impaired judgment, perseveration, personality change ("frontal lobe syndrome") |
| Other | Supplementary motor area | Bimanual coordination, motor initiation | Akinesia, alien hand syndrome (medial lesions) |
Parietal Lobe
| Domain | Area | Function | Deficit if Damaged |
|---|---|---|---|
| Sensory | Primary somatosensory cortex (S1, postcentral gyrus) | Conscious sensation - touch, pain, proprioception of contralateral body | Contralateral cortical sensory loss (astereognosis, graphesthesia loss, 2-point discrimination loss) |
| Sensory | Superior parietal lobule | Spatial orientation, body schema | Contralateral sensory neglect |
| Other | Inferior parietal lobule (dominant) | Language comprehension (angular gyrus), reading, writing, calculation | Gerstmann syndrome (agraphia, acalculia, finger agnosia, left-right disorientation) |
| Other | Inferior parietal lobule (non-dominant) | Visuospatial processing, attention to contralateral space | Hemispatial neglect, constructional apraxia, dressing apraxia, anosognosia |
Temporal Lobe
| Domain | Area | Function | Deficit if Damaged |
|---|---|---|---|
| Sensory | Primary auditory cortex (Heschl's gyri, BA 41/42) | Conscious hearing | Bilateral damage causes cortical deafness; unilateral causes subtle deficits |
| Sensory | Wernicke's area (dominant, BA 22) | Auditory language comprehension | Receptive (Wernicke's) aphasia - fluent but meaningless speech, paraphasias |
| Other | Hippocampus (medial temporal) | Memory consolidation, declarative memory | Anterograde amnesia (bilateral damage) |
| Other | Amygdala | Emotional processing, fear | Kluver-Bucy syndrome (bilateral: hypersexuality, hyperorality, placidity, visual agnosia) |
| Other | Inferior temporal gyrus | Visual object recognition | Visual agnosia, prosopagnosia (face recognition) |
| Other | Temporal lobe (general) | Seizure generation in epilepsy | Complex partial seizures with automatisms, aura (deja vu, olfactory hallucinations) |
Occipital Lobe
| Domain | Area | Function | Deficit if Damaged |
|---|---|---|---|
| Sensory | Primary visual cortex (V1, BA 17, calcarine sulcus) | Conscious vision | Contralateral homonymous hemianopia (with macular sparing in PCA occlusion) |
| Other | Visual association cortex (V2-V5) | Color, motion, depth perception | Achromatopsia (color blindness), motion blindness, visual agnosia |
| Other | Bilateral occipital damage | All conscious vision | Anton's syndrome (cortical blindness with denial of blindness) |
2. INTERNAL CAPSULE
| Domain | Part | Function | Deficit if Damaged |
|---|---|---|---|
| Motor | Posterior limb (anterior 2/3) | Corticospinal tract (voluntary movement) | Pure motor hemiplegia - face, arm, leg equally affected |
| Motor | Genu | Corticobulbar tract (motor to cranial nerves) | Contralateral lower face weakness, dysarthria |
| Sensory | Posterior limb (posterior 1/3) | Thalamocortical sensory radiation | Pure sensory hemianesthesia |
| Other | Posterior limb | Optic radiation | Contralateral homonymous hemianopia |
Clinical pearl: Internal capsule lesions cause dense contralateral hemiplegia (face + arm + leg) because all fibers are compactly packed - a small lesion causes a large deficit.
3. THALAMUS
| Domain | Nucleus | Function | Deficit if Damaged |
|---|---|---|---|
| Sensory | VPL (ventroposterolateral) | Relays sensory from contralateral body (spinothalamic + dorsal columns) | Contralateral hemisensory loss, thalamic pain (Dejerine-Roussy syndrome) |
| Sensory | VPM (ventroposteromedial) | Relays sensory from face (trigeminal) | Contralateral facial sensory loss |
| Sensory | LGN (lateral geniculate) | Visual relay | Visual field defects |
| Sensory | MGN (medial geniculate) | Auditory relay | Hearing deficits (subtle) |
| Motor | VA/VL (ventroanterior/ventrolateral) | Relay from cerebellum and basal ganglia to motor cortex | Contralateral tremor, ataxia |
| Other | Pulvinar + LP | Higher sensory integration, attention | Neglect, sensory inattention |
| Other | Anterior nucleus + MD | Memory, emotion (limbic relay) | Memory impairment (thalamic amnesia) |
| Other | Intralaminar nuclei | Arousal, consciousness | Decreased consciousness (bilateral damage = coma) |
4. HYPOTHALAMUS
| Domain | Function | Deficit if Damaged |
|---|---|---|
| Other | Temperature regulation | Hyperthermia or poikilothermia |
| Other | Appetite/satiety (lateral = hunger; ventromedial = satiety) | Anorexia or hyperphagia/obesity |
| Other | Osmolarity/ADH control (supraoptic nucleus) | Diabetes insipidus (loss of ADH) |
| Other | Circadian rhythm (suprachiasmatic nucleus) | Sleep-wake disturbance |
| Other | Autonomic control | Dysautonomia |
| Other | Endocrine control (via pituitary) | Panhypopituitarism, hormonal deficits |
5. BASAL GANGLIA
| Domain | Nucleus | Function | Deficit if Damaged |
|---|---|---|---|
| Motor | Striatum (caudate + putamen) | Motor planning, initiation, habit formation | Hypokinesia (Parkinsonism) or hyperkinesia (chorea, hemiballismus) |
| Motor | Substantia nigra (pars compacta) | Dopaminergic input, modulates movement | Parkinson's disease (rigidity, bradykinesia, rest tremor) |
| Motor | Subthalamic nucleus | Inhibitory control of movement | Contralateral hemiballismus if damaged (subthalamic nucleus lesion) |
| Motor | Globus pallidus | Output nucleus of BG | Dystonia, rigidity |
| Other | Caudate nucleus | Cognitive-motor integration | Cognitive slowing, abulia (anterior caudate) |
6. CEREBELLUM
| Domain | Part | Function | Deficit if Damaged |
|---|---|---|---|
| Motor | Lateral hemispheres (cerebrocerebellum) | Fine motor coordination of ipsilateral limbs | Ipsilateral limb ataxia, dysmetria, intention tremor, dysdiadochokinesia |
| Motor | Vermis (spinocerebellum) | Trunk and gait coordination | Truncal ataxia, wide-based gait (cerebellar gait) |
| Other | Flocculonodular lobe (vestibulocerebellum) | Balance, vestibulo-ocular reflex | Nystagmus, vertigo, balance problems |
| Other | Cerebellar lesions general | Speech coordination | Scanning/dysarthric speech ("staccato" speech) |
Key clinical point: Cerebellar deficits are ipsilateral to the lesion. There is NO paralysis, NO sensory loss, NO UMN signs.
7. BRAINSTEM
Midbrain
| Domain | Structure | Function | Deficit if Damaged |
|---|---|---|---|
| Motor | Cerebral peduncle (corticospinal) | Descending motor fibers | Contralateral hemiplegia |
| Motor | CN III nucleus + fascicles | Oculomotion: SR, IO, MR, IR + levator palpebrae; pupil constriction | Ipsilateral CN III palsy (ptosis, down-and-out eye, dilated pupil) |
| Other | Substantia nigra | (See BG) | Parkinsonism |
| Other | Periaqueductal gray (PAG) | Pain modulation, opioid receptors | Altered pain perception |
| Other | Superior colliculus | Vertical gaze center | Parinaud syndrome (upgaze palsy, convergence-retraction nystagmus, light-near dissociation) |
| Other | Red nucleus | Rubrospinal tract, motor coordination | Contralateral tremor/ataxia (Benedict syndrome) |
Crossed syndromes of midbrain:
- Weber syndrome: Ipsilateral CN III palsy + contralateral hemiplegia (peduncle)
- Benedict syndrome: Ipsilateral CN III palsy + contralateral tremor (red nucleus)
Pons
| Domain | Structure | Function | Deficit if Damaged |
|---|---|---|---|
| Motor | Corticospinal tract (basis pontis) | Descending motor | Contralateral weakness |
| Motor | CN VII nucleus | Lower motor neuron facial movement | Ipsilateral complete facial palsy (LMN type) |
| Motor | CN VI nucleus / PPRF | Horizontal gaze center | Ipsilateral conjugate gaze palsy (eyes deviate AWAY from side of lesion - opposite to cortical) |
| Sensory | CN V nucleus (main sensory) | Facial touch + proprioception | Ipsilateral facial sensory loss |
| Sensory | Spinothalamic tract | Contralateral body pain/temp | Contralateral body sensory loss |
| Sensory | Medial lemniscus | Contralateral body vibration/proprioception | Contralateral body loss |
| Other | CN V motor nucleus | Mastication | Ipsilateral jaw weakness, deviation toward lesion on opening |
| Other | CN VIII (cochlear nuclei) | Hearing | Ipsilateral deafness |
| Other | Locus coeruleus | Norepinephrine; arousal, attention | Altered consciousness, autonomic dysregulation |
| Other | Respiratory centers | Breathing | Apneustic or cluster breathing in pontine lesions |
Locked-in syndrome: Bilateral ventral pontine lesion - quadriplegia + anarthria, but consciousness preserved (patient communicates only by vertical eye movements or blinking).
Medulla
| Domain | Structure | Function | Deficit if Damaged |
|---|---|---|---|
| Motor | Pyramids (corticospinal) | Descending motor | Contralateral hemiplegia; decussation here |
| Motor | CN XII nucleus | Tongue movement | Ipsilateral tongue deviation TOWARD side of lesion (LMN) |
| Motor | CN IX, X, XI nuclei (nucleus ambiguus) | Swallowing, phonation, palate, SCM/trapezius | Dysphagia, dysphonia, palate deviation away from lesion, weak SCM |
| Sensory | Spinal trigeminal nucleus | Ipsilateral face pain + temp | Ipsilateral facial sensory loss (in lateral medullary syndrome) |
| Sensory | Spinothalamic tract | Contralateral body pain + temp | Contralateral body sensory loss |
| Sensory | Dorsal columns / medial lemniscus | Vibration, proprioception, fine touch | Contralateral body loss |
| Other | Nucleus solitarius | Taste, visceral sensory | Loss of taste (anterior 2/3 tongue via VII, posterior 1/3 via IX) |
| Other | Dorsal vagal nucleus | Parasympathetic to thoracic/abdominal viscera | Cardiac, GI dysfunction |
| Other | Sympathetic fibers | Descending sympathetics | Ipsilateral Horner syndrome (ptosis, miosis, anhidrosis) |
| Other | Inferior cerebellar peduncle | Cerebellum input | Ipsilateral ataxia |
| Other | Respiratory/cardiovascular centers | Breathing, HR, BP | Apnea (Ondine's curse - medullary respiratory center), Cheyne-Stokes respiration |
| Other | Vomiting center (area postrema) | Emesis | Nausea/vomiting |
Lateral medullary (Wallenberg) syndrome (PICA occlusion) - classic clinical case:
- Ipsilateral: facial pain/temp loss, Horner syndrome, limb ataxia, dysphagia, dysphonia
- Contralateral: body pain/temp loss
- NO motor weakness (motor fibers run medially, spared)
8. SPINAL CORD
Tracts Summary
| Tract | Location in Cord | Carries | Crosses |
|---|---|---|---|
| Lateral corticospinal | Lateral column | Motor (voluntary movement) | In medulla (pyramidal decussation) |
| Spinothalamic (anterolateral) | Anterior/lateral column | Pain, temperature, crude touch | Within 1-2 segments of entry (in cord) |
| Dorsal columns (posterior) | Posterior column | Vibration, proprioception, fine touch, 2-point discrimination | In medulla (sensory decussation) |
| Anterior corticospinal | Anterior column | Motor (axial/trunk, 10%) | At level of muscle innervated |
| Rubrospinal | Lateral column | Limb flexor tone | In midbrain |
| Vestibulospinal | Anterior column | Balance, extensor tone | Ipsilateral |
Spinal Cord Levels and Key Functions
| Level | Motor | Sensory | Reflex | Other |
|---|---|---|---|---|
| C3-C5 | Diaphragm (phrenic nerve) | - | - | Respiration - lesion above C3 = ventilator dependent |
| C5 | Shoulder abduction (deltoid), elbow flexion (biceps) | Lateral arm | Biceps reflex (C5-C6) | - |
| C6 | Wrist extension, supination | Lateral forearm, thumb | Brachioradialis reflex | - |
| C7 | Elbow extension (triceps), wrist flexion | Middle finger | Triceps reflex | - |
| C8 | Finger flexion (grip), intrinsics | Medial forearm, little finger | - | Horner syndrome (ciliospinal center C8-T2) |
| T1 | Intrinsic hand muscles | Medial arm | - | Ciliospinal center |
| T4 | - | Nipple level | - | - |
| T10 | - | Umbilicus | - | - |
| L1-L2 | Hip flexion (iliopsoas) | Inguinal region | Cremasteric reflex | - |
| L3-L4 | Knee extension (quadriceps) | Anterior thigh, medial leg | Knee jerk reflex (L3-L4) | - |
| L4-L5 | Ankle dorsiflexion, big toe extension | Medial dorsum of foot | - | - |
| S1 | Ankle plantar flexion (gastrocnemius) | Lateral foot, sole | Ankle jerk reflex (S1-S2) | - |
| S2-S4 | Anal sphincter, bladder | Perineum, saddle area | Bulbocavernosus reflex, anal wink | Micturition, defecation, erection |
Spinal Cord Syndromes (for CNS case)
| Syndrome | Lesion | Motor | Sensory | Other |
|---|---|---|---|---|
| Complete transection | All tracts at level | Bilateral UMN below + LMN at level | All modalities lost below | Autonomic: neurogenic bladder/bowel, sexual dysfunction |
| Brown-Sequard (hemisection) | One side of cord | Ipsilateral UMN below lesion; ipsilateral LMN at level | Ipsilateral: dorsal column loss (vibration/proprioception) below; Contralateral: spinothalamic loss (pain/temp) 1-2 levels below | Ipsilateral sympathetic loss |
| Central cord syndrome | Central (syrinx, hyperextension injury) | Upper limbs > lower limbs (cape distribution) | Dissociated sensory loss - pain/temp lost, vibration/proprioception spared (suspended sensory level) | Sacral sparing (outer spinothalamic fibers) |
| Anterior cord syndrome | Anterior spinal artery occlusion | Bilateral UMN motor loss below | Bilateral pain/temp loss below; vibration/proprioception PRESERVED | Bladder/bowel dysfunction |
| Posterior column syndrome (Subacute combined degeneration) | Posterior columns | No motor loss | Vibration/proprioception/fine touch lost; pain/temp preserved | Romberg positive, sensory ataxia |
| Conus medullaris | S2-S5 segments (conus) | Flaccid bladder/bowel; mild leg weakness | Saddle anesthesia | Bowel/bladder/sexual dysfunction - LMN type |
| Cauda equina | Lumbosacral nerve roots below L1 | Flaccid weakness of lower limbs | Saddle area, lower limbs (dermatomal) | LMN type bladder/bowel, radicular pain - NO UMN signs |
Quick Localization Cheat Sheet
| Feature | Cortex | Internal Capsule | Brainstem | Spinal Cord |
|---|---|---|---|---|
| Motor deficit | Contralateral; may be monoplegia | Contralateral dense hemiplegia (face=arm=leg) | Crossed (ipsilateral CN + contralateral body) | Bilateral below level; LMN at level |
| Sensory deficit | Cortical type, contralateral | Contralateral hemianesthesia | Crossed (alternating) | Dissociated or total below level |
| Cognitive/speech | Yes (cortex only) | May have aphasia | No | No |
| Cranial nerve signs | No direct CN palsy | No | Yes - hallmark of brainstem | No (except at foramen magnum) |
| Consciousness | Affected if bilateral | Can be affected | Midbrain/pontine lesions affect ARAS | Not affected |
| Seizures | Yes | Can occur | Rare | No |
| Ataxia | Mild with parietal | No | Yes (cerebellar pathways) | Yes (posterior column) |
UMN vs LMN - Essential Distinction
| Feature | UMN (above anterior horn) | LMN (anterior horn + nerve) |
|---|---|---|
| Tone | Increased (spasticity) | Decreased (flaccidity) |
| Reflexes | Hyperreflexia | Hyporeflexia/areflexia |
| Plantars | Extensor (Babinski positive) | Flexor (normal) |
| Wasting | Late, disuse atrophy only | Early, significant |
| Fasciculations | Absent | Present |
| Power | Reduced (pyramidal pattern) | Reduced (myotomal pattern) |
Autonomic (Other) Functions - Quick Reference
| Region | Sympathetic/Parasympathetic | Clinical Significance |
|---|---|---|
| Hypothalamus | Central integration of ANS | Dysautonomia, temperature dysregulation |
| Brainstem (dorsal vagal nucleus) | Parasympathetic to heart, lungs, gut | Bradycardia, GI dysmotility |
| T1-L2 lateral horn | Sympathetic preganglionic | Horner (T1), sweating, vasoconstriction |
| S2-S4 lateral horn | Parasympathetic to bladder, bowel, genitalia | Neurogenic bladder (reflex vs. areflexic), sexual dysfunction |
| Ciliospinal center (C8-T1) | Cervical sympathetics | Horner syndrome: ptosis + miosis + anhidrosis (ipsilateral) |
Sources: Adams & Victor's Principles of Neurology 12e | Localization in Clinical Neurology 8e | Guyton & Hall Medical Physiology | Gray's Anatomy for Students | Eric Kandel Principles of Neural Science 6e
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