Cerebellum

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LOCALIZATION

• Cerebellum
• NMJ
• Brachial Plexus, Median,
• Radial, and Ulnar nerves

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Cerebellum 17 cm x 120cm

• Anatomy
• Relation
• 3 Lobes
• Functional
• 4 deep nuclei
• fastigial
• Interposed x 2
• dentate
• Topography
• Blood supply

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• Vermis ? Ms mvt of the axial body
• The intermediate zone? distal portion of the
  limbs face
• The lateral zone has no topographic
  representation
• Input ? motor premotor areas of the frontal
  cortex somatosensory sensory ass. area of the
  parietal cortex
• ? overall planning coordination of rapid
  sequential mvts ? Incoordination

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Functions

• Timing, in rapid progression
• Intensity of muscle contraction
• Continuously updated info.
• Makes corrective adjustments when actual mvt
  unfavorably compares with the intended
• Performs most of the damping function
• Aids the C.Cx in planning next mvt ? smooth
  progression
• Ballistic mvts typing, guitar ? loss of
  automaticity
• Control the interplay b/n agonist antagonists,
  synergists fixators
• Extramotor predictive function- rate of
  progression of auditory and visual phenomenon

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Afferent pathways ?Brain

• Corticopontocerebellar Pathway? to lat zone
• Olivocerebellar tract? to all areas
• Vestibuloc. fibers? floculonod lobe Fastigial
  N.
• Reticulocerebellr fibers? vermis

?Periphery

• Dorsal spinocerebellar tract ? vermis IM zone?
  same side
• From ms spindles and somatic
• Ventral spinocerebellar tract fastest
• SCP? Both side
• By Motor signals arriving at AHC efference copy
  of the ant horn motor drive

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Major Efferent pathways

• Midline ?fastigial N. ? medullary pontine?
  fastigiobulbar C.reticular tracts
• Equilibrium apparatus vestibular N. ? Equil.
• Reticular formation? postural attitude
• IM zone ?interposed N?C. reticular C. .olivery
  fs
• Thalamus ?Cx, ? BG, ? to the red N and RF
• Coordinate reciprocal contraction of limbs ms
• Lateral zone?dentate N. ? thalamus ? Cx?
  Dentatothalamic Dentatorubral fs
• ?coordination of sequential motor activity

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Summary It controls motor fn at 3 level

• The Vestibulocerebellum archicerebellum
• ? floculonodular adjacent vermis
• ? Equilibrium and postural mvts
• The Spinocerebellum paleocerebellum
• ? IM zone ? comparison ? interposed N ?corrective
  signal
• Smooth coordinated mvt of agonist and antagonist
  ms of distal limb for acute purposeful patterned
  mvt
• Damping ballistic mvt fn
• Cerebrocerebellum Neocerebellum
• ?Lateral zone dentate N
• Extreme incoordin. of cx purposeful mvts of
  hands,fingers, feet of speech apparatus
• Planning Timing of sequential mvts
• Extramotor predictive function

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Clinical Abnormalities

• Small lesion / ? !/2 removed
• Imbalance and Ataxia
• Truncal ataxia? wide based gait
• Not lateralized /- Symmetric nystagmus ? toxic,
  metabolic, inflammatory or neurodegenerative dis.
• Asymmetric ataxia ? structural dis. Ischemia,
  tumor or mass lesion
• Visual cues
• C. limb ataxia
• Dysmetria
• Dysdiadochokinesia
• Tremor
• Past pointing / rebound
• C. nystagmus
• Hypotonia
• Dysarthria

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Cerebellar Syndromes

• The Rostral Vermis Sundrome ant.lobe
• Wide-based stance and gait
• Ataxia of Gait vs. heel-to shin
• Arm coordination? Nl/impaired
• Hypotonia/nystagmus/dysarthria ? infrequent
• ?Cerebellar cortical degeneration of Chr.
  Alcoholics
• Ant sup vermis

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• Caudal Vermis Synd Floculonodular post lobe
• Axial dysequilibirium staggering gait
• Little or no limb ataxia
• /- nystagmus rotated head posture
• S/S of Inc ICP
• ?medulloblastoma

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• Cerebellar Hemispheric Synd
• Mvts requiring fine coord. ms controlled by the
  precentral cx
• ?Infarcts, neoplasm, and abscesses
• Pancerebellar Syndrome
• Trunk, limbs, cranial ms
• Infectious and parainfectious, Hypoglycemia,
  hyperthermia, paraneoplastic d/o, and other
  toxic-metabolic d/os

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Syndromes of cerebellar infarction

• Thrombotic or embolic
• Limb gait ataxia, dysarthria, nyst, altered
  mental sttus
• With/without BS and 4th vent compression
• Large? occiputal headache vetigo, N/V, gait
  unsteadiness and dysarthria, ? obst hydrocephalus
• ? neck stiffness,
• Herniation? CR sx VS. MB compression
• ?PICA, SCA or both
• Border zone ? not easily localizable
• 47 pts cardiac arrest 4, Atheroma or
  hypercoagulable state 20, Large art VB
  occlusive dis. 34, Brain embolism 23,
  unknown mechanism 19

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Approach

• Hx ? Duration, Neurologic Sx, Alcohol,
  Nutritional
• Exam sensory/ motor
• Evaluation for Vit. B12 def.
• Imaging studies

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Neuromuscular Junction Dis.

• Fatigable/ ptosis, diplopia or bulbar weakness
• Proximal weakness
• Normal mental fn,
• Fluctuating
• Ms tone/Reflexes/Atrophy
• Most often gradual

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• Major causes of intermittent generalized weakness
  are
• Electrolyte disturbances
• Ms disorders channelopathies, metabolic defects
• NMJ disorders MG, LEMS
• Myopathic ? proximal and are rarely limited to
  the limbs
• Proximal weakness of 2/4 limbs? ms, less
  commonly, NMJ or AHC
• Myopathy? pelvic or shoulder girdle ms
• NM disorders such as MG ? Proximal weakness ass
  with ptosis,diplopia or bulbar weakness
  fluctuating in severity during the day
• The proximal weakness of AHC dis? asymmetric
• ? Numbness is absent in all
• ? sensation is intact

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Myasthenia Gravis

• Autoantibody? anti AchR
• The most common 1 in 7500
• Fatigable weakness
• The cranial ms? Early
• Diplopia, ptosis, Chewing, speech, regurgitation,
  aspiration
• 85 ? generalized
• DTR sensation? preserved
• Response to Tx, RNS

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DDX

• Neurasthenia ? nonorganic
• Drug induced myasthenia
• LEMS? presynaptic/ auto Ab against Ca
  channels85
• Often ass with malignancy
• Hyper-/hypothyroidism? inc. myasthenic weakness
• Graves disease VS. ocular MG
• Botulism? pupil and Incremental RNS
• Intracranial mass lesion
• Congenital myasthenic syndrome

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The Brachial Plexus

• C5-T1 ? to the entire UL shoulder and neck ms
• root, trunk, division, cords and branches.
• 5 major nerves Axillary, Radial posterior,
  Musculocutaneous Lateral, Ulnar medial and
  Median lateral Medial
• Plexopathy? Diffuse ? focused study of PNs
• Radiculopthy? sensation is spared
• Most B.P ?regional involvement ?localizing to the
  specific region in the B.P ?1st step? then easy

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• General rules
• Weakness in a myotomal pattern
• ?C8 to T1 ms?lower trunk/medial cord
• ?C5 and C6 ms ? upper trunk/lateral cord
• ?isolated to a single nr is unlikely to be of
  plexus origin,
• ?Invt of ms innervated by Radial axill nr?Post
  cord
• ?Isolated middle trunk?unheard? C7 radiculopathy
• ?Fixed sensory loss extending into the medial
  forearm ? lower trunk/medial cord plexopathy
  sensory loss extending into the lat forearm ?
  upper trunk/lateral cord plexopathy

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• ?Weakness of the serratus anterior? radiculopathy
  or a component
• Specific disorders of the brachial plexus
• Downward movement of the shoulder results in an
  upper trunk disorder (Erb's palsy)
• hyperabduction causes a lower trunk injury
  (Klumpke's palsy).
• Lower trunk plexopathy? by compression ? TOS

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• Upper trunk plexopathies ?may ff surgical
  intervention in the region of the neck.
• Lower trunk plexopathies also can occur after
  chest-splitting cardiothoracic surgery.
• Compression by tumors/masses ? lower trunk
  plexopathies from Pancoast tumors
•   Backpack palsy patients often present with
  arm/shoulder weakness after wearing a backpack
  for a prolonged period of time, suggestive of a
  predominantly upper trunk lesion. Some sensory
  loss is also present.

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• RADICULOPATHY
• Structural spine disease of the cervical spine
  remains one of the most frequent problems
  affecting the upper extremities.
• In the young individual with an acute herniated
  disc, severe radiating pain, sensory loss, and
  weakness in muscles of the myotome of the
  affected nerve root can be present.
• In the elderly- acute herniation of discs is
  uncommon? cervical spondylosis 2o to disc
  degeneration, calcification,? more frequent
  --.they often present present with more diffuse
  pain, sensory loss, and weakness. ? involvement
  of multiple myotomes
• Head turning, coughing, or sneezing may
  exacerbate symptoms, regardless of age.
• C7 radiculopathies ? 70. C6 n 19 to 25 C8 in
  4 to 10 and C5 in 2 .

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• C5 radiculopathy Sry loss?proximal lat arm.
  Weakness ? shoulder muscles including deltoid
  and biceps brachii . Biceps reflex- lost
• C6 radiculopathy Sry loss ?lat forearm and
  digit 1 of the hand. Weakness?biceps and
  brachioradialis, deltoid, pronator teres, and
  triceps minimally. Biceps and brachioradialis
  reflex? lost
• C7 radiculopathy Sry loss? digits 2 to 4, with
  digit 3 most affected. Weakness? triceps , wrist
  flexors, pronator teres, and wrist extensors.
  Triceps reflex ?lost.
• C8 radiculopathy Sry loss? digit 5, medial
  hand, and medial forearm. Weakness? finger
  flexors, thumb abduction, interossei, and finger
  extensors.

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• MEDIAN NERVE SYNDROMES
• Pronator teres syndrome rare
• Entrapment ?in the proximal forearm ? physically
  active .
• Forearm pain and sry loss over entire lateral
  palm. Sry loss over the thenar eminence? typical,
  Vs. from carpal tunnel syndrome
• Anterior interosseous neuropathy ? br around the
  elbow. ? innervates the flexor pollicis longus,
  the deep flexors of digits 2 and 3, and pronator
  quadratus.? not sry O/E cannot make a standard
  "O"

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• ULNAR NERVE SYNDROMES
• At the elbow Ulnar neuropathy is the 2nd most
  common compression neuropathy.? sry loss and
  paresthesias over digits 4 and 5. worsened grip
  and clumsiness. plus weakness in finger and
  wrist flexion. A prominent Tinel's sign
• Epicondylar groove?the Tardy ulnar palsy
• Entrapment as it enters the cubital tunnel
• At the wrist? same finding finger flexers

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• RADIAL NERVE SYNDROMES
• At the spiral groove ? ffs prolonged pressure .
  "Saturday night palsy"
• O/E? the triceps is OK the wrist, finger
  extensors, and brachioradialis are weak. Sry loss
  over the dorsum of the hand, possibly extending
  up the posterior forearm. Thumb abduction is
  affected as abductor pollicis longus is a
  radial-innervated muscle.
• Posterior interosseous neuropathy nerve
  branches off just proximal to the elbow and
  innervates the extensor muscles of the forearm?
  O/E medial deviation of the wrist

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The End