Physiology · Year 1 · from Physiology
Case 1: Horner Syndrome - Sympathetic Pathway Disruption
Clinical Image
Source: Wikimedia Commons - Horner's Syndrome and Autonomic innervation - CC BY-SA 4.0
Patient Presentation
A 58-year-old male smoker presents to the emergency department with a 2-week history of right-sided drooping eyelid and decreased sweating on the right side of his face. He also reports persistent right shoulder pain radiating down his arm for the past month. He has lost 15 pounds unintentionally over 3 months and notes a new chronic cough. He denies headache, trauma, or recent neck manipulation.
Demographics
- Age: 58 years
- Sex: Male
- Risk factors: 40 pack-year smoking history
- Duration: 2 weeks of eye symptoms, 1 month of shoulder/arm pain
Chief Complaint
Right-sided ptosis, decreased facial sweating, and shoulder/arm pain
Physical Examination
- Vital signs: BP 138/86, HR 78, RR 16, Temp 37.0C
- HEENT:
- Right eye: Ptosis (2mm), miosis (constricted pupil), anisocoria more pronounced in dim light
- Right face: Anhidrosis (decreased sweating) on right forehead and face
- No enophthalmos apparent
- Pupillary light reflex intact bilaterally
- Neurological: Decreased sensation in C8-T1 distribution on right, 4/5 grip strength right hand
- Respiratory: Decreased breath sounds in right apex
- Lymph nodes: Right supraclavicular lymphadenopathy
Workup
- Cocaine eye drops (4%): Right pupil fails to dilate (confirms Horner syndrome - cocaine blocks norepinephrine reuptake; requires intact sympathetic pathway)
- Hydroxyamphetamine drops (1%): Right pupil fails to dilate (indicates postganglionic lesion - this drug releases stored norepinephrine from intact postganglionic neurons)
- Chest X-ray: Right apical mass
- CT chest with contrast: 4 cm mass in right lung apex invading chest wall, consistent with Pancoast tumor
- MRI brachial plexus: Tumor invasion of lower brachial plexus (C8-T1) and stellate ganglion
- CT-guided biopsy: Non-small cell lung carcinoma (squamous cell)
Diagnosis
Pancoast Tumor (superior sulcus tumor) causing Horner Syndrome and brachial plexus involvement
Treatment
- Oncology consultation for staging workup (PET scan, brain MRI)
- Multidisciplinary tumor board discussion
- If resectable: Neoadjuvant chemoradiation followed by surgical resection
- Pain management: Neuropathic pain regimen (gabapentin, opioids as needed)
- Smoking cessation
- Palliative care involvement for symptom management
- Eye care: Artificial tears (if decreased tear production)
Physiological Principles Demonstrated
- Sympathetic pathway anatomy: The three-neuron sympathetic pathway to the eye: (1) First-order neuron: hypothalamus to ciliospinal center at C8-T2; (2) Second-order neuron: exits spinal cord, passes over lung apex, synapses in superior cervical ganglion; (3) Third-order neuron: travels with internal carotid to orbit.
- Horner syndrome triad:
- Ptosis: Loss of sympathetic input to Mueller's muscle (superior tarsal muscle) causes mild ptosis (2-3mm, less than CN III palsy)
- Miosis: Loss of sympathetic input to the dilator pupillae muscle causes relative miosis; unopposed parasympathetic tone constricts the pupil
- Anhidrosis: Loss of sympathetic input to facial sweat glands; distribution depends on lesion location (face and neck for pre-ganglionic; forehead only for post-ganglionic)
- Pharmacological localization: Cocaine test confirms Horner (blocks NE reuptake, requiring intact pathway); hydroxyamphetamine test localizes to postganglionic if pupil fails to dilate (releases stored NE from intact postganglionic neurons)
- Dual innervation of the pupil: Pupil size reflects balance between parasympathetic (constrictor, via CN III) and sympathetic (dilator) tone. Loss of one reveals unopposed action of the other.
- Pancoast syndrome: Apical lung tumors can involve the lower brachial plexus (C8-T1 causing hand weakness and Klumpke-type sensory loss), stellate ganglion (causing Horner syndrome), and parietal pleura (causing shoulder/arm pain).