Neurology JC022: Where Is The Lesion? (2) Symptoms And Signs In Neurology

Question 1

Spinal cord

Answer 1

Cervical: C1-8
Thoracic: T1-12
Sacral: S1-5

Plexuses (nerve roots join together)
- Brachial plexus (upper limbs): **C5-T1
- Lumbosacral plexus (lower limbs + pelvic structures): **L1-S3

Conus medullaris: End at ***L1/2 spinal level —> Cauda equina (nerve roots of lower spinal cord)

Ventral root: Motor (anterior horn cells)
Dorsal root: Sensory (1st order neuron in dorsal root ganglion)
Spinal root: Ventral + Dorsal root

Radiculopathy: Nerve root lesion
Myelopathy: Cord lesion

Revision: Organisation of Spinal nerves
Spinal cord
—> Spinal nerve roots (Dorsal + Ventral root)
—> Spinal nerve
—> Branch (Dorsal + Ventral rami + Rami communicantes (gray / white rami —> leads to sympathetic ganglion))

Question 2

Pyramidal system

Answer 2

• Use to find out location of lesion
• Corticobulbar
• Corticospinal

UMN lesion (**Primary motor cortex —> Cranial motor nuclei (brainstem) / Anterior horn cells (spinal cord)):
- no early wasting
- **weakness (spastic paresis)
- **↑ tone (spasticity)
- **hyperreflexic
- ***Babinski’s sign

LMN lesion (Cranial motor nuclei (brainstem) / Anterior horn cells (spinal cord) —> NMJ):
- **wasting +/- **fasciculation
- **weakness (flaccid paresis)
- ↓ tone (flaccid)
- **hyporeflexic / areflexic

Question 3

Primary motor cortex homunculus

Answer 3

Medial side of cortex: Contralateral Leg
Lateral side of cortex: Contralateral Hands, Head and Neck

Question 4

General localisation

Answer 4

1. Pyramidal system (Corticospinal / Corticobulbar)
   Weakness depending on level of lesion:

Brainstem
- specific CN deficit (i.e. head and neck)
- **UMN signs below level of lesion (e.g. spastic quadriplegia)
- other signs depending on intrinsic structures in Brainstem (e.g. MLF: **internuclear ophthalmoplegia, sympathetic tract: ***ipsilateral Horner)

Spinal cord
- head and neck spared
- above C5: **UMN signs below level of lesion (e.g. spastic quadriplegia)
- C5-T1: **LMN signs upper limb, **UMN signs lower limb
- T2-T12: **sensory level on trunk, upper limbs spared, UMN signs lower limb
- L1-S5: upper limbs spared, **LMN signs lower limb, **sphincter disturbance (Cauda equina affected)

Question 5

Myotomes

Answer 5

Diaphragm: ***C3-5

Hands / Arms:
Deltoid: C5-6
Biceps, Brachialis: C5-6
Triceps: C6-**7
Extensor carpi radialis longus + breves: C6-7
Instrinsic hand muscles: **C8-T1

Legs:
Iliopsoas: L1-2
Adductor longus + brevis: L2-3
Quadriceps: **L3-4
Hamstrings: L4-5
Tibialis anterior: **L4-5
Gastrocnemius, Soleus: S1-2
Extensor hallucis longus: L5-S1

Anal sphincter
Sphincter ani externus: ***S2-4

Question 6

Dermatome

Answer 6

No C1 dermatome (∵ no sensory root)
Head:
- Face: CN5
- Occipital: Spinal nerves (C2, C3)
- Shoulder: Spinal nerves (C4)

Dermatomes overlap!

Special dermatomes:
**T10: Umbilicus
**L1: Inguinal region

Question 7

***Spinal cord

Answer 7

Spinal cord level
- Motor:
—> **At level of lesion: LMN sign
—> **Below level of lesion: UMN sign
—> Above level of lesion: Unaffected
- Sensory: ***Dermatomal sensory level
- Different specific deficits depending on area of affected spinal cord

Spinal root
- Motor: **LMN signs
- Sensory: **Dermatomal sensory level
- Cauda equina (multiple root levels, sphincter affected)

Plexus:
- ***Multiple nerves affected
- Motor: LMN signs
- Sensory: Dermatomal sensory level

(Dermatomal sensory level: intact dermatome level located immediately above the first dermatome level with impaired or absent light touch or pin prick sensation)

Question 8

***Peripheral nerves

Answer 8

• ***LMN signs
• Usually all sensory modalities affected but some more than others (e.g. in DM)

Generalised neuropathy (i.e. **Polyneuropathy)
- Motor:
—> LMN signs in upper + lower limbs
—> **Distal > Proximal weakness
—> Respiratory muscles may be affected (e.g. **Guillain-Barré syndrome)
- Sensory: **Glove + Stocking sensory deficit (唔再係Dermatomal sensory level, ∵ length-dependent, longest peripheral nerve affected first, ∴ sphincters relatively spared due to innervation by short nerves)

**Isolated compressive neuropathy
- Motor: LMN signs of **specific muscle group affected
- Sensory: ***Dermatomal sensory deficit (of nerve distribution) (同Polyneuropathy唔同)

Question 9

NMJ

Answer 9

• Weakness (eyelid, external ocular muscles, respiratory, pharyngeal, neck, jaw, limbs)
• ***No sensory deficit
• **Diurnal variation (weakness during later of day) + **Fatiguability

E.g. Myasthenia gravis
- **Ptosis
- **Thymoma
- **Dysphagia: aspiration pneumonia
- **Ventilatory failure

Question 10

Muscle (Myopathy)

Answer 10

• Weakness (***Proximal > Distal, ∵ more muscle in proximal area) —> difficulty climbing up stairs / standing up from squatting
• Symmetrical
• ***No sensory deficit
• may not have wasting
• may have Muscle ***Pain + Tenderness

E.g. Musculodystrophy

Question 11

What is the lesion?

Answer 11

Congenital / Developmental
- younger age group
- positive family history
- consanguineous birth

Vascular
- **sudden onset
- **transient nature
- risk factors of vascular disease

Degenerative
- older age group
- **gradual onset
- **progressive course

Neoplastic / Paraneoplastic
- **insidious onset
- **progressive course
- other generalised features e.g. loss of weight / appetite

Demyelinating
- ***exacerbating / remitting course

Inflammatory (Infective / Autoimmune)
- fever (acute / chronic)
- general malaise
- ***signs of infection / inflammation e.g. LN, skin rash, joint pains

Metabolic / Toxic
- precipitating course e.g. drugs, exacerbation of previous systemic disorder (e.g. liver / renal encephalopathy)
- encephalopathy

Trauma / Physical
- cause and effect usually seen

Location of lesion, Spectrum, Pattern of clinical features also give clues to nature of lesion