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Neurology > Neuroanatomy > Flashcards

Neuroanatomy Flashcards

1
Q

In the spinal cord, what does the dorsal (poster), lateral and anterior horn consist of?

A

Anterior horn: lower motor neurons
Posterior horn (dorsal): sensory neurons
Lateral horn: cell bodies of preganglionic sympathetic neurons

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2
Q

Spinothalamic tract

A
  • Made of second order neurons
  • Consists of the anterior spinothalamic tract (crude touch and pressure) and lateral spinothalamic (pain and temperature) tract carries information of crude touch, pressure, pain, and temperature.
  • Primary sensory neurons for pain and temperature initially synapse at the dorsal horn grey matter.
  • Second order neurons then send axons/fibres to cross in the ventral (anterior) white commissure to enter the contralateral anterolateral pathway as spinothalamic tract.
  • Decussation occurs over 2-3 segments whilst ascending.
  • Then to the 3rd neuron in the ventral posterolateral nucleus of the thalamus –> somatosensory cortex (post-central gyrus - parietal lobe)
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3
Q

Blood supply of the spinal cord

A
  • Vertebral arteries arise from the subclavian artery

Branches

  • Anterior spinal artery (a single anterior spinal artery): supply the anterior 2/3 of spinal cord and lower medulla
  • Posterior spinal artery (2 paired posterior spinal arteries): supply the posterior part of the spinal cord, primarily posterior columns
  • Arterial vasocorona: anastomosis between spinal arteries

Spinal arteries are further fed by:

  • Intercostal branches of the aorta in the midthoracic region
  • Great radicular artery (of Adamkiewicz) in the lower thoracic or lumbar region
  • Posterior spinal artery receives flow from multiple branches
  • Anterior spinal artery has fewer, but larger, anterior radicular arteries feeling into it - prone to ischaemia
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4
Q

Dorsal columns

A
  • Made up of fibres of primary sensory neurons
  • Cell bodies located in ipsilateral dorsal root ganglion
  • Gracile fasciculus: transmit fine touch, vibration and proprioception from the LL (below T6 or T7 and below). Terminates in the gracile nucleus of the medulla
  • Cuneate fasciculus: transmit fine touch, vibration, proprioception from the UL (T6 and above). Terminates in the cuneate nucleus of the medulla
  • From gracile and cuneate nuclei, fibres project to contralateral ventral posterolateral nucleus of thalamus via medial lemniscus then to somatosensory cortex (post-central gyrus)
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5
Q

Spinocerebellar tract

A

Posterior spinocerebellar, anterior spinocerebellar, spino-olivary tract: LL proprioception to cerebellum

Cuneocerebellar: UL propioception to cerebellum

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6
Q

Corticospinal tract (part of pyramidal tract) - descending tract

A

Function: voluntary movement of the contralateral side

  • Fibers of the pyramidal tract originate from the primary motor cortex (precentral gyrus) and descend ipsilaterally to the brain stem via the internal capsule.
  • The fibers descend from the brainstem as two divisions of the corticospinal tract.
  • Lateral corticospinal tract: Approximately 80% of these fibers decussate at the level of the medulla (pyramidal decussation) to the contralateral side to form the lateral corticospinal tract. They then descend into the spinal cord to innervate the limbs and digits.
    Controls the precision and speed of skilled movements involving the distal muscles of the ipsilateral limbs, particularly those of the hands and fingers.
  • Anterior corticospinal tract: The remaining approximately 20% of fibers descend from the brainstem ipsilaterally, forming the anterior corticospinal tract. These decussate at the spinal level of the trunk muscles they innervate
    Controls skilled voluntary movements involving the trunk and proximal limb muscles
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7
Q

Features of central cord syndrome

A

Aetiology:

  • syringomyelia
  • spinal cord compression
  • hyperextension injury (eg: car crash) associated with chronic cervical spondylosis

Affected spinal tracts
- Bilateral central corticospinal tracts and lateral spinothalamic tract

Clinical features 
- Sensory deficits 
Bilateral paresis
Upper > lower limbs
Distal >proximal
  • Bilateral crossing spinothalamic fibers passing in the anterior commissure affected
  • Anterolateral tracts themselves are spared, sensation above and below the lesion remains intact, leading to a “suspended” sensory level
  • Sensory is seen in a “Cape and vest” distribution across neck and the shoulders/trunk
  • As central lesion enlarges, affects anterior horn cells causing segmental LMN at the level of the lesion
  • Further expansion affects the lateral corticospinal tract causing UMN weakness and temperature and sensation loss below the lesion
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8
Q

Features of anterior cord syndrome

A

Etiology
- Occlusion of anterior spinal artery (ischaemic)

Affected spinal tracts: corticospinal and spinothalamic tracts (dorsal columns spared)

Clinical features:

  • Bilateral motor paralysis below the level of the lesion
  • Loss of pain and temperature and autonomic dysfunction below the level of the lesion
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9
Q

Posterior cord syndrome

A

Etiology

  • Trauma (penetrating injury)
  • Occlusion of the posterior spinal artery (rarely ischaemic given bilateral blood supply)
  • MS
  • Normally demyelination, nutritional, genetic

Affected
- Dorsal columns

Clinical feature:
- Bilateral loss of proprioception, vibration and touch below the level of the lesion

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10
Q

Brown sequard syndrome

A

Etiology:

  • Trauma (eg: penetrating injury)
  • Spinal cord compression

Affected: hemisection of the cord

Clinical features
Ipsilateral:
- Segment flaccid paralysis at the level of the lesion (ipsilateral LMN weakness and complete sensory loss at level of lesion) due to affecting the anterior horn cells
- Spastic paralysis below the level of the lesion and ipsilateral Babinski sign (ipsilateral UMN weakness below the level of the lesion)
- Loss of proprioception, vibration, tactile discrimination below the level of the lesion
- Horner syndrome in lesions above T1

Contralateral:
Loss of pain and temperature sensation from 1-2 segments below the lesion

Bladder dysfunction does not occur because this requires bilateral disruption of descending autonomic pathways and in brown sequard it is only unilateral involvement.

Ipsilateral corticospinal
Contralateral spinothalamic

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11
Q

What are the extrapyramidal tracts

A

Rubrospinal
Reticulospinal
Vestibulospinal
Tectospinal

Involved in involuntary movement (eg: equilibratory reflexes, visual + auditory reflexes)
Muscle tone

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12
Q

Diseases of the anterior horn

A

Occur secondary to spinal muscular atrophy, polio

Cause progressive bilateral paresis

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13
Q

Tabes dorsalis

A

Progressive bilateral loss of proprioception, vibration and touch sensation due to syphillis

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14
Q

Features of vitamin B 12 deficiency

A

Loss of propioception, vibration, touch sensation, ataxia and persistent paraesthesia

Degeneration of dorsal columns and lateral column

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15
Q

Difference between corticospinal vs cauda equina syndrome

A
  • When injury to the corticospinal tracts occurs, spastic
    paresis or paralysis is possible, manifesting as weakness, hyperreflexia, muscle spasms, and extensor plantar responses (UMN)
    • Involvement of the distal spinal cord and lower roots
    (cauda equina syndrome) can involve weakness of the
    LMN, with decreased muscle tone and areflexia. Loss of anal tone is specific for cauda equina.
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16
Q

Spinal cord compression

A
  • High-dose intravenous administration of glucocorticoids within the first 8 hours of traumatic spinal cord injury improves outcomes.
  • Urgent surgical decompression followed by glucocorticoids and radiation therapy is typically required to treat spinal cord compression due to metastatic disease.
  • Radiosensitive tumor types, such as leukemia, lymphoma, myeloma, and germ cell tumors, often may be treated urgently with radiation therapy alone.
17
Q

Which tumours are most likely to metastasize to brain?

A

lung
breast
melanoma

18
Q

Primary CNS Lymphoma

A
  • Primary CNS lymphoma (PC SL) is a non-Hodgkin lymphoma that can affect any part of the CNS but commonly
    presents as a focal supratentorial lesion.
  • Visual symptoms are
    common because of frequent tumor involvement of the optic
    radiations. PCNSL most commonly affects immunocomprorniscd
    patients but can occur in patients with intact immune
    systems.
  • An association with the Epstein-Barr virus has been noted.
  • Pathologic analysis, usually of a brain biopsy specimen.
    is required to make a diagnosis of PCNSL.
  • Diffuse large
    B cell lymphoma is typical.

Tx: methotrexate, radiation

19
Q

Meningioma

A

Meningiomas are benign tumors that arise from the meningeal coverings of the brain.
- They are the most common extraaxial (that is, not in the brain parenchyma) intracranial lesion in adults; other extraparenchymal tumors include schwannomas.
- Meningiomas are typically slow-growing
tumors that often are discovered incidentally: clinical signs
generally are subtle.
- These tumors have characteristic imaging
features. including intense homogeneous contrast
enhancement (‘“lightbulb” sign), areas of calcification, and a dural tail which is thickening of the dura adjacent to the
mass

20
Q

Treatment for brain mets

A

Patients with multiple brain metastases typically are
treated with whole-brain radiation, whereas those with a single brain metastasis are usually candidates for surgical
resection

21
Q

Oculomotor nerve palsy

A
  • Downward and outward deviation of eye (down and out) due to unopposed actions of the lateral rectus and superior oblique muscles.
  • Weakness of the levator palpebrae superioris muscle results in ptosis,
  • Mydriasis due to impairment of parasympathetic function
  • Horizontal diplopia that worsens when turning the gaze away from the affected side

NOTE: parasympathetic fibers are affected by compression first

• Compression of 3rd nerve - the parasympathetic fibres are affected first causing a dilated pupil
○ Herniating from malignant MCA, the first thing it pushes on is the parasympathetic fibres which causes a “blown” dilated pupil and thus this is compression affecting the parasympathetic fibres.

In diabetes, the artery is affected (infarct), there is a 3rd nerve palsy with sparing of the pupil as there is no compression

22
Q

Trochlear nerve palsy

A
  • Trochlear nerve palsy causes paralysis of the ipsilateral superior oblique muscle.
  • Inability to depress and abduct the eyeball simultaneously leading to hypertropia (upwards deviation) that increases in adduction, slight limitation of abduction, and excyclotorsion (outward rotation) of the affected eye - up and out
    -Diplopia
    § Vertical or oblique diplopia
    § Exacerbated on downgaze (e.g., reading, walking downstairs) away from side of affected muscle
    § Worsens when patient turns the head towards the paralyzed muscle (ipsilateral)→ compensatory head tilt to the opposite side of the lesion
23
Q

Trochlear Nerve Palsy

A
  • Trochlear nerve palsy causes paralysis of the ipsilateral superior oblique muscle.
  • Inability to depress and abduct the eyeball simultaneously leading to hypertropia (upwards deviation) that increases in adduction, slight limitation of abduction, and excyclotorsion (outward rotation) of the affected eye - up and out
  • Diplopia
    § Vertical or oblique diplopia
    § Exacerbated on downgaze (e.g., reading, walking downstairs) away from side of affected muscle
    Worsens when patient turns the head towards the paralyzed muscle (ipsilateral)→ compensatory head tilt to the opposite side of the lesion

You cannot look to the floor

24
Q

Abducens Nerve Palsy

A
  • Horizontal diplopia that worsens when looking at distant objects
  • Medial deviation of the affected eye at primary gaze
  • Inability to abduct the eye (affected individuals will rotate the head to look to the side)
25
Q

Cavernous sinus lesion

A

CN III, CN IV, CN V1, CN V2, and CN VI

  • Impaired movement of the eye: paralysis of extraocular muscles (CN III, CN IV, CN VI)
  • Horner syndrome
  • Decreased sensation of the upper face (CN V1, CN V2)
26
Q

Visual field defects

A

Homonymous hemianopia
• incongruous defects: lesion of optic tract
• congruous defects: lesion of optic radiation or occipital cortex
• macula sparing: lesion of occipital cortex

Homonymous quadrantanopias*
• superior: lesion of the inferior optic radiations in the temporal lobe (Meyer’s loop)
• inferior: lesion of the superior optic radiations in the parietal lobe
• mnemonic = PITS (Parietal-Inferior, Temporal-Superior)

Bitemporal hemianopia
• lesion of optic chiasm
• upper quadrant defect > lower quadrant defect = inferior chiasmal compression, commonly a pituitary tumour
• lower quadrant defect > upper quadrant defect = superior chiasmal compression, commonly a craniopharyngioma

27
Q 
51yo female presented with weakness of R hand. Right finger and wrist drop with loss of thumb extension. Power normal, nil sensory deficit. All tendon reflexes symmetrical. What is the most likely cause of her hand weakness?
A. C7 radiculopathy
B. Left hemispheric lacunar infarct 
C. Posterior interosseous nerve palsy
D. Radial nerve palsy
E. Thoracic outlet syndrome
A

C. Posterior interosseous nerve palsy

Posterior Interosseus Nerve: purely motor
Superficial radial nerve: sensory to anatomic snuffbox
Radial nerve palsy would have: Wrist drop, loss of Brachioradialis reflex, sensory changes

28
Q

Winging of the scapula leads to which lesion?

A

Long thoracic nerve which supplies the serratus anterior muscle
C5/6/7 roots

29
Q

In which part of the brain is the control of appetite regulated?

A

Arcuate nucleus of hypothalamus

30
Q

Cauda Equina vs Spinal Cord Compression

A
  • Compression can also occur due to compromise of spinal stability due to vertebral metastases and compression from associated fractures.
  • Cauda equina syndrome is the same process but occurring at or below the level of the cauda equina (typically at the level of L1)
  • Both usually presents with pain and weakness and should be treated the same way

Cord compression causes an upper motor neuron (UMN) pattern of weakness
Cauda equina causes an with lower motor neuron (LMN) pattern, compression of nerve roots

Neurology (11 decks)

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