Which sympathetic ganglion causes Horner's syndrome in lung cancer?

Stellate Ganglion Causes Horner's Syndrome in Lung Cancer

In lung cancer, Horner's syndrome is primarily caused by infiltration of the sympathetic chain and stellate ganglion, particularly in superior sulcus (Pancoast) tumors. 1 This occurs when tumors at the apex of the lung invade the surrounding structures, interrupting the oculosympathetic pathway.

Anatomical Basis of Horner's Syndrome in Lung Cancer

Oculosympathetic Pathway

• The sympathetic pathway to the eye consists of a three-neuron circuit:
  1. First-order (central) neurons: originate in hypothalamus and descend to spinal cord
  2. Second-order (preganglionic) neurons: exit spinal cord at T1-T2 level and ascend to superior cervical ganglion
  3. Third-order (postganglionic) neurons: travel from superior cervical ganglion along carotid artery to the eye

Mechanism in Lung Cancer

• Superior sulcus tumors specifically invade the stellate ganglion, disrupting the sympathetic chain 1
• The stellate ganglion (first thoracic ganglion) contains the sympathetic fibers that control pupillary dilation and eyelid elevation 2
• Interruption at this level causes the classic triad of Horner's syndrome:
  • Ptosis (drooping eyelid)
  • Miosis (constricted pupil)
  • Anhidrosis (lack of facial sweating)

Clinical Presentation in Lung Cancer

Pancoast Syndrome Components

• Horner syndrome (unilateral ptosis, miosis, and lack of facial sweating) from infiltration of the sympathetic chain and stellate ganglion 1
• Shoulder and arm pain related to invasion of the brachial plexus
• Weakness, pain, and paresthesias in the distribution of C8-T2 nerve roots 1

Diagnostic Considerations

• Horner's syndrome may be the initial presenting sign of lung cancer 3, 4
• The syndrome is often incomplete in lung cancer cases, with varying degrees of the classic triad 5
• Superior sulcus tumors typically cause preganglionic Horner's syndrome by affecting the sympathetic pathway before it reaches the superior cervical ganglion 6

Imaging Evaluation

Recommended Imaging

• CT scan of the chest with contrast is the initial imaging modality of choice to evaluate for apical lung tumors 6
• MRI provides excellent anatomic detail of superior sulcus tumors and their relationship to surrounding structures 1
• PET scanning helps determine the extent of disease and presence of metastases 4

Imaging Findings

• Superior sulcus tumors may initially appear as apical pleural thickening on chest radiographs 1
• CT and MRI can detect small lesions that may be hidden behind the first rib 1
• Tumors are classified as anterior, middle, or posterior compartment based on their location relative to the scalene muscles 1

Management Implications

Prognostic Significance

• The presence of Horner's syndrome in lung cancer indicates local invasion and often a more advanced stage 1
• Invasion of the stellate ganglion is a negative prognostic factor that may limit surgical options 1

Treatment Approach

• Multimodality treatment is typically required for superior sulcus tumors with Horner's syndrome 6
• Preoperative radiotherapy followed by surgical resection is a common approach 1
• Complete resection of the tumor with negative margins is the goal when feasible 1

Clinical Pearls

• Horner's syndrome without respiratory symptoms should raise suspicion for a superior sulcus tumor due to the peripheral location of these tumors 1
• The distribution of symptoms outside the chest (arm pain, neurological symptoms) may delay consideration of lung cancer as the primary etiology 1
• Pharmacological testing (cocaine test, apraclonidine) can confirm the diagnosis of Horner's syndrome but doesn't typically identify the level of lesion in lung cancer cases 6
• Other causes of Horner's syndrome (carotid dissection, stroke) should be ruled out when appropriate 6

In summary, the stellate ganglion is the key sympathetic structure whose invasion by lung cancer (particularly superior sulcus tumors) leads to Horner's syndrome. Recognition of this syndrome should prompt thorough evaluation for an underlying apical lung tumor.