Disorders of Somatic Sensation

1
Disorders of Somatic Sensation

• Refer to Chapter 6 of
• Clinical Neurology Textbook

2
Disorders of Somatic Sensation

• Review of Anatomy, History, the Sensory
  Examination
• Reading assignment
• Read pages 200-203

3
Disorders of Somatic Sensation

• Sensory Changes
• Peripheral Nerve Lesions
• Mononeuropathy
• Lesion of a single nerve usually d/t entrapment
• Sensory loss in minimal
• Polyneuropathy
• Stocking-and-Glove Sensory loss
• Symmetric
• Distal gt Proximal
• Nerve Root
• Modality loss is dermatomal
• Possible myotomal weakness

4
Disorders of Somatic Sensation

• Sensory Changes
• Cord Lesions (Figs 6-5, 6-6, 6-7)
• Central
• Causes syringomyelia, cord tumors, trauma
• Bilateral asymmetrical loss of pain temp
• Anterolateral
• Contralateral loss of pain temp
• Anterior
• Weakness paralysis

5
Disorders of Somatic Sensation

• Sensory Changes
• Cord Lesions (Figs 6-5, 6-6, 6-7)
• Post Column
• Loss of viration, proprioception, 2-pt
  discrimination
• Cord Hemisection
• AKA Brown-Sequards Syndrome
• Loss of spinothalamic tracts, Post Columns,
  Pyramidal tracts

6
Disorders of Somatic Sensation

• Sensory Changes
• Brainstem Lesion
• General
• Dorsolateral MO Pons
• Crossed Sensory Deficit Loss of spinothalmic
  tract modalities contralateral limbs trunk and
  ipsilateral face
• Above the Spinal Trigeminal Nucleus
• Loss of spinothalamic tract modalities
  contralateral side of the body
• Medial Lemniscus
• Contralateral loss of posterior columns

7
Disorders of Somatic Sensation

• Sensory Changes
• Thalamic Lesion
• Loss or impairment of all modalities of sensation
  on the half of the body contralateral to the
  lesion
• Any form of cutaneous stimuli leads to a painful
  or unpleasant sensation
• May outlast the stimulus for a longer period of
  time than normal

8
Disorders of Somatic Sensation

• Sensory Changes
• Sensory Cortical Lesion
• All Modalities are affected
• Deep gt Superficial
• Contralateral/Unilateral loss of modalities
• Limbs gt Face Trunk
• Superifical Lesions
• Localized affects distal gt proximal
• Recovery
• 2-pt usually permanently affected

9
Disorders of Somatic Sensation

• Polyneuropathies
• Acute Idiopathic Demyelinating Polyradiculoneuropa
  thy
• AKA Guillain-Barre Syndrome
• Types
• Demyelinating Form
• Axonal Form
• AMSAN acute motor-sensory axonal neuropathy
• AMAN acute motor axonal neuropathy

10
Disorders of Somatic Sensation

• Polyneuropathies
• Acute Idiopathic Demyelinating Polyradiculoneuropa
  thy
• Pathophysiology
• Autoimmune Disorder All Forms
• Demyelinating Form predilection for NR Distal
  PN
• Hallmark inflammatory lesions
  well-circumscribed areas containing lymphocytes
  macrophages
• Demyelination
• Axonal Damage - some

11
Disorders of Somatic Sensation

• Polyneuropathies
• Acute Idiopathic Demyelinating Polyradiculoneuropa
  thy
• Pathophysiology
• Axonal Form
• NR affected gt PN
• Wallerian Degeneration degeneration occurs from
  site of the lesion distally (away from cell body)
  

12
Disorders of Somatic Sensation

• Polyneuropathies
• Acute Idiopathic Demyelinating Polyradiculoneuropa
  thy
• Epidemiology
• Rare 1-2 per 100,000
• Age any, but higher incidence in the elderly
  population
• Demyelinating form accounts for 90 of all cases
  in North America, Europe, Australia
• Antecedent Events (triggers)
• Occur 1-3 weeks prior
• URI
• Vaccines rabbiies esp
• Viral infections HIV esp
• Epstein-Barr virus
• Cytomegalic Virus
• Bacterial Infections
• Surgery

13
Disorders of Somatic Sensation

• Polyneuropathies
• Acute Idiopathic Demyelinating Polyradiculoneuropa
  thy
• Clinical Features
• Cardinal Features
• Paresthesias involves the toes and fingers
  symmetrically initially
• Weakness not a presenting feature
• Hypo or Areflexia one of the earliest S/S

14
Disorders of Somatic Sensation

• Polyneuropathies
• Acute Idiopathic Demyelinating Polyradiculoneuropa
  thy
• Clinical Features
• Other Features
• Poorly localized deep pain
• Sensory changes seen infrequently, but posterior
  columns most affected
• Progression
• Progressive Phase 3-4 wks
• Plateau Phase 2-4 wks before recovery begins

15
Disorders of Somatic Sensation

• Polyneuropathies
• Acute Idiopathic Demyelinating Polyradiculoneuropa
  thy
• Diagnosis (Table 6-3)
• Required for Diagnosis
• Progressive muscle weakness
• Loss of DTRs
• Clinical Studies
• CSF Inc protein w/ normal cell count
• NAD in 1st week
• EMG marked dec of motor sensory conduction

16
Disorders of Somatic Sensation

• Polyneuropathies
• Diabetes Mellitus
• A metabolic and nutritional neuropathy
• Affects
• CNS
• PNS Cranial Nerves

17
Disorders of Somatic Sensation

• Polyneuropathies
• Diabetes Mellitus
• Neurological Complications of the CNS
• Glycemic Extremes
• Hypoglycemia adrenergic neurolglycopenic
  symptoms are experienced
• Hyperglycemia - Type I or II, 3 Ps
  (poly-dipsia, phagia, uria)
• Stroke ? incedence severity
• Encephalopathy

18
Disorders of Somatic Sensation

• Polyneuropathies
• Diabetes Mellitus
• Neurological Complications of the CNS
• Atheroma
• Degeneration or thickening of arteries
• Arteriolar Capillary Microangiopathy
• Pseudotabes Diabteica d/t infarction of the
  spinal cord
• Affects the dorsal root ganglia degeneration of
  post columns

19
Disorders of Somatic Sensation

• Polyneuropathies
• Diabetes Mellitus
• Neurological Complications of the PNS CN
• Peripheral nerve involvement is common
• MC is a mixed polyneuropathy presentation (70)
• Primary sensory polyneuropathy (30)

20
Disorders of Somatic Sensation

• Polyneuropathies
• Diabetes Mellitus
• Neurological Complications of the PNS CN
• Three Common Manifestations
• Polyneuropathy Sensory or Mixed, Dx by ? DTRs
  vibratory sensation loss in the legs
• Mononeuropathy Multiplex Neuropathy in separate
  parts of the body, characterized by pain
  weakness
• Mononeuropathy Simplex pain is the MC feature
• Diabetic Amyotrophy
• Muscular atrophy

21
Disorders of Somatic Sensation

• Mononeuropathies (Appendix C)
• Median Nerve Compression
• AKA Carpal Tunnel Syndrome
• Causes
• Pregnancy, Trauma (RSS), Degenerative Arthritis,
  Tenosynovitis
• Clinical Features
• Early pain paresthesia in median nerve
  distribution, pain _at_ night
• Late weakness atrophy with impaired cutaneous
  sensation

22
Disorders of Somatic Sensation

• Mononeuropathies
• Ulnar Nerve Dysfunction
• Causes
• External Pressure
• Cubital Tunnel Syndrome
• Cubitus Valgus Deformity
• Clinical Features
• Paresthesia, hypesthesia, nocturnal pain in the
  little finger and ulnar border of the hand
• Elbow pain
• Sensory loss Muscle weakness ulnar aspect of
  hand
• Pain exacerbated by elbow flexion

23
Disorders of Somatic Sensation

• Mononeuropathies
• Radial Nerve Compression
• Causes
• Compression of the radial nerve in the axilla
• Clinical Features
• Motor primarily
• Sensory occasionally

24
Disorders of Somatic Sensation

• Mononeuropathies
• Thoracic Outlet Syndrome
• Causes
• Cervical Rib
• Scalene Compression
• Costoclavicular Syndrome
• Clinical Features
• C8/T1 dermatome
• Pain
• Paresthesia
• Resembles CTS

25
Disorders of Somatic Sensation

• Mononeuropathies
• Peroneal Nerve Lesions
• Causes
• Secondary to trauma or pressure over thee fibula
  head
• Clinical Features
• Weakness or paralysis
• Toe Extension
• Foot eversion
• Impaired Sensation
• Dorsum of the foot
• Distal, ant aspect of the leg

26
Disorders of Somatic Sensation

• Mononeuropathies
• Lateral Femoral Cutaneous Nerve Dysfunction
• AKA Meralgia Paresthetica
• Causes
• Entrapment as it passes through the inguinal
  ligament
• Pregnancy
• Obese patients
• Tight belt
• Excessive angulation of femur
• Clinical Features
• A pure sensory entrapment
• Numbness, painful burning itching in the
  lateral thigh
• Hypesthesia to touch pinprick