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Extra-Adrenal Paraganglia (EAP)

Extra-Adrenal Paraganglia (EAP): Anatomy, Function, and Clinical Significance

Anatomy and Distribution

Extra-adrenal paraganglia (EAP) are neuroendocrine tissues derived from neural crest cells, forming part of the autonomic nervous system. They are distributed symmetrically from the skull base to the pelvic floor and include:

• Sympathetic EAP: Located in the posterior mediastinum, retroperitoneum, and along the aortic axis (e.g., organs of Zuckerkandl near the inferior mesenteric artery). These produce catecholamines (epinephrine/norepinephrine) and function similarly to the adrenal medulla.
• Parasympathetic EAP: Found in the head, neck, and anterior mediastinum (e.g., carotid body, jugulotympanic region). These act as chemoreceptors and rarely secrete hormones.

Key Functions

• Sympathetic EAP: Mediate the “fight-or-flight” response via catecholamine release.
• Parasympathetic EAP: Detect changes in blood oxygen, carbon dioxide, and pH (e.g., carotid body regulates respiration).

Clinical Conditions: Paragangliomas

Paragangliomas are rare tumors arising from EAP. Key features include:

• Functional tumors: Secrete catecholamines, causing episodic hypertension, headaches, palpitations, and sweating.
• Non-functional tumors: Present as painless masses or incidental findings.
• Locations:
  • Head/neck: Carotid body, glomus jugulare, vagal paragangliomas.
  • Thorax/abdomen: Aorticopulmonary, retroperitoneal (e.g., organ of Zuckerkandl).
• Imaging features:
  • CT: Homogeneous or heterogeneous hyperenhancing mass.
  • MRI: “Salt-and-pepper” appearance (flow voids + T2 hyperintensity).
  • MIBG/PET–CT: Functional imaging for metastatic evaluation.

Genetic and Syndromic Associations

Up to 40% of cases are linked to germline mutations, including:

• SDHx mutations (SDHB, SDHD): High risk of malignant transformation.
• MEN2, von Hippel-Lindau (VHL), NF1: Associated with pheochromocytomas/paragangliomas.
• Carney-Stratakis syndrome: Gastric stromal tumors + paragangliomas.

Diagnosis and Management

1. Biochemical Testing: Elevated plasma/urine metanephrines for functional tumors.
2. Histopathology: “Zellballen” pattern (nests of chief cells surrounded by sustentacular cells).
3. Treatment:
   • Surgical resection: Primary curative approach.
   • Preoperative embolization: For highly vascular tumors.
   • Medical management: Alpha/beta-blockers for catecholamine excess.
   • Radiation/chemotherapy: For metastatic or inoperable cases.

Prognosis

• Benign tumors: Excellent outcomes after resection.
• Malignant tumors (10–20%): Poor prognosis, especially SDHB-mutant cases.

Summary Table: Key Features of EAP and Paragangliomas

Feature	Sympathetic EAP	Parasympathetic EAP
Location	Retroperitoneum, posterior mediastinum	Head/neck, anterior mediastinum
Function	Catecholamine secretion	Chemoreception
Common Tumors	Functional paragangliomas	Non-functional paragangliomas
Imaging	CT/MRI hyperenhancement	Salt-and-pepper on MRI
Genetic Links	SDHx, VHL, NF1	SDHx, RET (MEN2)

Consult with Our Team of Experts Now!
At DrStemCellsThailand (DRSCT)‘s Anti-Aging and Regenerative Medicine Center of Thailand, we emphasize comprehensive evaluations and personalized treatment plans of Cellular Therapy and Stem Cells for managing various health conditions. If you have questions about Extra-Adrenal Paraganglia (EAP) or would like more information on our services, consult with our experts today!

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References:

• AJR Imaging Features of Extraadrenal Paragangliomas13
• NCI Treatment Guidelines4
• Histopathology and Genetic Syndromes25

EAP-related paragangliomas require multidisciplinary management, emphasizing genetic testing, tailored imaging, and surgical expertise to optimize outcomes.