12 Acute Peripheral Neurologic Disorders, part 1

Question 1

Remarks on peripheral nervous system (PNS) lesions

Answer 1

1. The PNS serves sensory, motor, and autonomic functions. Thus, the patient with a peripheral nerve lesion may have deficit in any combination of these functions.
2. Exclude central processes, such as stroke or spinal cord injury, before considering an acute peripheral lesion

Question 2

Finding suggestive of CNS disease

Answer 2

Hallmarks of cortical disease:
- aphasia (vs dysarthria)
- apraxia
- vision loss (vs diplopia)
Upper motor neuron signs
- hyperreflexia
- hypertonia (spasticity)
- extensor plantor (Babinski) reflexes

Question 3

What is Hoffman’s sign

Answer 3

an involuntary flexion movement of the thumb and or index finger when the examiner flicks the fingernail of the middle finger down

Question 4

Remarks on patients at risk for diaphragmatic failure

Answer 4

measure baseline forced vital capacity or negative inspiratory pressure to assess whether there is an immediate need for respiratory support or admission to ICU

Question 5

General disposition for acute peripheral disorders

Answer 5

Admit if there’s
- potential respiratory or autonomic compromise
- or if they present with severe or rapidly progressing weakness
If a peripheral disorder is suspected and the patient does not require admission, arrange for neurologic follow-up within 7 to 10 days

Question 6

Examples of acute peripheral neuropathies

Answer 6

GBS
Bell’s palsy
Ramsey Hunt syndrome (Herpes Zoster Oticus)
Acute neuropathies of Lyme Disease

Question 7

What is GBS

Answer 7

Guillain-Barré syndrome
1. An acute polyneuropathy characterized by immune-mediated peripheral nerve myelin sheath or axon destruction.
2. The prevailing theory is that antibodies directed against myelin sheath and axons of peripheral nerves are formed in response to a preceding viral or bacterial illness
3. Symptoms are at their worst in 2 to 4 weeks, and recovery can very from weeks to a year

Question 8

Clinical features of GBS

Answer 8

1. Preceded by a viral illness
2. Ascending symmetric weakness
3. areflexia or hyporeflexia

Question 9

More common form of GBS in Asia

Answer 9

Axonal form
- motor paralysis with sensory function intact

Question 10

triad of Miller-Fisher syndrome

Answer 10

Ophthalmoplegia
Ataxia
Areflxia

Question 11

CSF findings in GBS

Answer 11

Cytoalbuminoogic dissociation
- low white cell (<10 cells/mm3, monocytic)
- high protein (>45 mg/dL)

When there are >100 cells/mm3, other considerations include HIV, syphilis, tuberculous/bacterial meningitis

Question 12

First step in management of GBS

Answer 12

Assessment of respiratory function
A well-estbalished monitoring parameter is vital capacity, with normal values ranging from 60 to 70 mL/kg.
A simple bedside assessment of respiratory status is obtained by trending values reached when the patient counts from 1 to 25 with a single breath.

Question 13

Remarks on intubation in GBS

Answer 13

Avoid depolarizing neuromuscular blockers like succinylcholine due to the risk of hyperkalemic response

Question 14

Indications for intubation in GBS patients

Answer 14

Vital capacity <15 mL/kg
Declining one breath count
PaO2 <70 mm Hg on room air
Bulbar dysfunction (DOB, swallowing, or speech)
Aspiration

Question 15

Indications for ICU admission in GBS patients

Answer 15

Autonomic dysfunction
Bulbar dysfunction
Capacity (Vital) <20 mL/kg
Decrease of >30% of VC/negative inspiratory force
Enability to ambulate
Flasmafaresis treatment (plasmapharesis)

Question 16

Treatment of GBS

Answer 16

IV IMMUNOGLOBULIN
- More widely available and less cumbersome to administer
- associated with thromboembolism and aseptic meningitis

PLASMA EXCHANGE
- associated with hemodynamic instability and small increased rate of relapse (although full recovery is still more likely)

Neither is superior to the other
nor are they more efficacious if used together
Corticosteroids are of NO benefit and may be HARMFUL

Question 17

Most common cause of unilateral facial paralysis

Answer 17

Bell’s paralysis
* Facial nerve palsy
* Facial numbness or hyperestesia can be present
* Subtle dysfunction of CN V, VIII, IX, X may be associated

Question 18

Most important alternative diagnoses to exclude in Bell’s palsy

Answer 18

ear infections and stroke
EAR INFECTIONS
- r/o malignant otitis and mastoiditis
STROKE
- sensory loss of all contralateral to the affected cortex
- brainstem stroke may have ipsilateral gaze palsy due to ischemia of the abducens nucleus. So, test extraocular muscle function in all patients suspected of having Bell’s palsy

Question 19

Treatement of Bell’s Palsy

Answer 19

Steroids + antivirals.
RCTs suggest benefit of combination over steroid alone.
+/- eye patch or ocular lubricants

Question 20

Prognosis in Bell’s Palsy

Answer 20

Most patients begin to recover within 3 weeks but about 15% will have permanent paralysis.
Ensure follow-up within 7 days with a primary care physician or otolarygologist

Question 21

What is Ramsey Hunt syndrome

Answer 21

Herpes zoster oticus
Herpes zoster infection of the geniculate ganglion
Presents with unilateral facial nerve palsy, severe pain, and a vesicular eruption on the face or in the auditory canal.
Ramsey Hunt syndrome may be indistinguishable from Bell’s palsy if paralysis precedes the vesicular eruption.
When active herpes zoster is suspected, prescribe both steroids and antivirals

Question 22

Consider Lyme disease as the causative agent in patients with facial palsy and

Answer 22

erythema migrans, tick bite, or arthritis
CSF - mononuclear pleocytosis

Question 23

Treatment of Lyme disease

Answer 23

Doxycycline 100 mg twice daily for 14 to 21 days
Facial nerve palsies in lyme disease represent secondary stage of illness and require 1 month treatment of doxycycline
or amoxicillin, cefuroxime, ceftriaxone, or azithromycin