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GBS – Guillain Barre Syndrome – Pathophysiology, types, symptoms, diagnosis

Pathophysiology

Myelin is a complex substance that covers nerves, providing insulation and speeding the conduction of impulses from the cell body to the dendrites. The cell that produces myelin in the peripheral nervous system is the Schwann cell. In Guillain-Barre the Schwann cell is spared, allowing for remyelination in the recovery phase of the disease.

Guillain-Barre is the result of a cell-mediated immune attack on peripheral nerve myelin proteins (Ho & Griffin, 1999). The best-accepted theory is that an infectious organism contains an amino acid that mimics the peripheral nerve myelin protein. The immune system cannot distinguish between the two proteins and attacks and destroys peripheral nerve myelin. Studies indicate that an exact location within the peripheral nervous system, the ganglioside GM1b, is the most likely target of the immune attack (Yuki, Ang, Koga et al., 2000). With the autoimmune attack there is an influx of macrophages and other immune-mediated agents that attack myelin, cause inflammation and destruction, and leave the axon unable to support nerve conduction.

Guillain-Barre Syndrome Disability Score.

0 = Healthy state

1 = Minor symptoms and capable of running

2 = Able to walk 10 m or more without assistance but unable to run

3 = Able to walk 10 m across an open space with help

4 = Bedridden or chair bound

5 = Requiring assisted ventilation for at least part of the day

6 = Dead

Subtypes of Gullain- Bare Syndrome

Several subtypes of GBS are recognized reflecting differnces in the pattern and symptoms of peripheral nerve involvement. The most common are acute inflammatory demyelating demyelinating polyneuropathy (AIDP), acute motor axonal neuropathy (AMAN), acute motor sensory axonal neuropathy (AMSAN), and Miller-Fischer syndrome (MFS).

Acute Inflammatory Demyelinating Polyneuropathy

  • Most common presentation
  • Weakness and numbness begin in the legs, then progress upward to the trunk, arms, and cranial nerves.
  • Motor: paresis to quadriplegia, deficits are symmetric
  • Sensory: mild numbness, which is worse in toes.
  • Reflexes: diminished or absent
  • Respiratory : respiratory insufficiency occurs in about 50% of patients
  • Electrophysiologic diagnosis: demyelinating disease.

Acute Motor Axonal Neuropathy

  • Affects children and young adults.
  • Identical to ascending GBS, except sensory signs and symptoms are absent.
  • May be mild form of ascending GBS.
  • Muscle pain is generally not present.
  • Electrophysiologic diagnosis: axonal involvement.

Acute Motor Sensory Axonal Neuropathy

  • Affects mostly adults
  • Motor: initial weakness in the brainstem cranial nerves (facial, glossopharyngeal, vagus and hypoglossal nerves) then weakness progress downwards.
  • Sensory: numbness occurs distally, more often in the hands than in the feet.
  • Often rapid respiratory involvement.
  • Electrophysiologic diagnosis: axonal involvement.

Miller- Fischer Syndrome

  • Rare (5% of patients with GBS)
  • Affects adults and children
  • Seen as a triad of ophthalmoplegia, ataxia, and areflexia
  • Usually no sensory loss
  • Electrophysiologic diagnosis: demyelinating disease.

Clinical manifestations

Classic Guillain-Barre begins with muscle weakness and diminished reflexes of the lower extremities.

  • Hyporeflexia and weakness progress and may result in quadriplegia.
  • Demyelination of the nerves that innervate the diaphragm and intercostal muscles results in neuromuscular respiratory failure.

Sensory symptoms include paresthesias of the hands and feet and pain related to the demyelination of sensory fibers.

Cranial nerve demyelination can result in a variety of clinical manifestations.

  • Optic nerve demyelination may result in blindness.
  • Bulbar muscle weakness related to demyelination of the glossopharyngeal and vagus nerves results in an inability to swallow or clear secretions.
  • Vagus nerve demyelination results in autonomic dysfunction, manifested by instability of the cardiovascular system.
  • The presentation is variable and may include tachycardia, bradycardia, hypertension, or orthostatic hypotension.
  • The symptoms of autonomic dysfunction occur and resolve rapidly.

Guillain-Barre does not affect cognitive function or level of consciousness. While the classic clinical features include areflexia and ascending weakness. There may be a sensory presentation, with progressive sensory symptoms, an atypical axonal destruction, and the Miller-Fisher variant, which includes paralysis of the ocular muscles, ataxia, and areflexia.

Diagnosis

History and neurologic exam

  • Diagnosis is based on the clinical presentation. The required diagnostic criteria for GBS include progressive weakness of two or more limbs due to neuropathy, areflexia.
  • A history of a viral illness in the previous few weeks suggests the diagnosis.
  • Progressive weakness, decreased sensation, decreased deep tendon reflexes.

Changes in vital capacity and negative inspiratory force are assessed to identify impending neuromuscular respiratory failure.

Diagnostic evaluation

  • Lumbar puncture: Elevated protein levels are detected in CSF evaluation, without an increase in other cells.
  • Electrophysiologic studies: Nerve conduction velocity shows decreased conduction velocity of peripheral nerves.

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