Neuroscience · Year 2 · from Neuroscience
Case 2: Lower Motor Neuron Lesion (Guillain-Barre Syndrome)
Patient Presentation
Demographics: 34-year-old female
Chief Complaint: Progressive weakness in legs and arms over 5 days
History of Present Illness: The patient noticed tingling in her feet 8 days ago. Over the following days, she developed weakness in her legs, making it difficult to climb stairs. The weakness has ascended to involve her hips and is now affecting her arms. She had a respiratory infection with diarrhea 2 weeks before symptom onset. She feels short of breath when lying flat.
Systematic Neurological Examination:
Mental Status:
- Fully alert and oriented; cognition intact
Cranial Nerves:
- II-VI: Intact
- VII: Bilateral facial weakness - unable to fully close eyes, cannot puff cheeks or whistle; forehead also weak bilaterally (LMN pattern)
- IX, X: Mild dysphagia; weak cough
- XI-XII: Intact
Motor Examination:
- Inspection: No atrophy (too acute); no fasciculations
- Tone: DECREASED throughout (flaccid); limbs feel "floppy" on passive movement
- Strength (MRC scale):
- Proximal upper extremities: 4/5 bilaterally (shoulder abduction, elbow flexion)
- Distal upper extremities: 4+/5 bilaterally (wrist extension, grip)
- Proximal lower extremities: 3/5 bilaterally (hip flexion, knee extension)
- Distal lower extremities: 3/5 bilaterally (ankle dorsiflexion, plantarflexion)
- Pattern: Symmetric, ascending weakness; proximal = distal
Sensory Examination:
- Light touch: Decreased in stocking distribution to mid-calf, glove distribution to wrists
- Vibration: Decreased at toes, intact at ankles
- Proprioception: Mildly impaired at toes bilaterally
- Pain/temperature: Mild decrease distally
Reflexes:
- Biceps: ABSENT bilaterally (0)
- Triceps: ABSENT bilaterally (0)
- Brachioradialis: ABSENT bilaterally (0)
- Patellar: ABSENT bilaterally (0)
- Achilles: ABSENT bilaterally (0)
- Babinski: ABSENT bilaterally (flexor/no response - toes stay still)
Coordination:
- Finger-to-nose: Intact but weak
- Heel-to-shin: Unable to perform adequately due to weakness
Gait:
- Unable to stand without assistance
- Steppage gait pattern when attempting to walk (high knee lift to clear floppy foot)
Respiratory Assessment:
- Forced vital capacity (FVC): 1.8 L (predicted 3.4 L) - 53% of predicted
- Negative inspiratory force (NIF): -28 cm H2O (concerning if less than -30)
Summary of LMN Findings:
- Weakness with DECREASED tone (flaccidity)
- ABSENT reflexes (areflexia)
- NO Babinski sign
- Facial weakness including forehead (LMN pattern bilaterally)
- Sensory involvement in peripheral distribution
Workup:
- Lumbar puncture: Protein 185 mg/dL (elevated), WBC 3 (normal) - albuminocytologic dissociation
- Nerve conduction studies: Prolonged distal latencies, conduction block, reduced amplitudes - demyelinating pattern
Diagnosis: Guillain-Barre syndrome (acute inflammatory demyelinating polyradiculoneuropathy)
Treatment:
- ICU admission for respiratory monitoring
- IVIG 0.4 g/kg/day for 5 days
- Prophylactic DVT prevention
- Pain management
- Close monitoring of FVC and NIF (intubation if FVC <1L or NIF >-20)
Clinical Pearl: LMN lesions produce the opposite pattern from UMN lesions: weakness with decreased tone (flaccidity), diminished or absent reflexes, and (over time) atrophy and fasciculations. In Guillain-Barre syndrome, the areflexia is often the most striking early finding. The ascending pattern and facial weakness are characteristic. Respiratory failure is the major life-threatening complication, requiring close monitoring of FVC.