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Parathyroid Disorders


KEY FACTS

Terminology

  • CNS manifestations related to parathyroid hormone (PTH) metabolic abnormalities

    • Hyperparathyroid (HPTH); hypoparathyroid (HP)

Imaging

  • Bilateral symmetric calcifications in globi pallidi, putamen, caudate nuclei

  • Diffuse patchy “salt & pepper” lesions in skull in primary HPTH

  • Plaque-like dural calcification, “pipestem” calcifications of carotid arteries in secondary HPTH

  • Brown tumors: Focal expansile lytic lesions with nonsclerotic margins in primary HPTH and secondary HPTH

  • T2WI: Hypointensity involving basal ganglia, cerebral cortex, or dentate nucleus due to Ca++ deposition

Top Differential Diagnoses

  • Fahr disease

  • Physiologic calcification

  • Congenital HIV

  • Hypoxic-ischemic encephalopathy

Pathology

  • Primary HPTH: Parathyroid adenoma (75-85%), parathyroid hyperplasia (10-20%), carcinoma (1-5%), ↑ PTH, ↑ Ca++

  • Secondary HPTH: Chronic renal failure, kidney fails to convert vitamin D to active form and excrete phosphate

  • HP: Parathyroids are absent or atrophied; genetic autoimmune syndrome or DiGeorge syndrome (total absence of PT glands at birth)

  • PHP: Insensitivity of end-organ to PTH, rather than decreased production of PTH

Clinical Issues

  • HPTH: ↑ Ca++ affects transsynaptic nerve conduction, fatigue, pain, nausea, osteoporosis

  • HP: Carpal-pedal spasm, tetany, seizure, and hyperreflexia

Axial NECT in primary hyperparathyroidism shows extensive patchy lytic
and sclerotic areas
involving the calvaria. This gives a classic salt and pepper appearance of the calvaria.

Axial NECT in a patient with a long history of dialysis for chronic renal failure demonstrates classic changes in skull due to secondary hyperparathyroidism. There is extensive calcification of the tentorium
, sclerosis of calvaria
, and pipe-like calcification of the internal carotid arteries
.

Axial NECT in a patient with hypoparathyroidism shows symmetric bilateral basal ganglia calcifications
. Focal calcifications are also seen in the subcortical white matter
.

Axial T1 MR in the same patient shows T1 shortening in the basal ganglia
due to calcifications. Calcium deposition in the basal ganglia is seen in both hyper- and hypoparathyroidism. Additional sites for calcium deposition include thalamus, subcortical white matter, dentate nuclei, and dura.

TERMINOLOGY

Definitions

  • CNS manifestations related to parathyroid hormone (PTH) metabolic abnormalities

    • 1° and 2° hyperparathyroidism (HPTH)

    • Hypoparathyroidism (HP)

    • Pseudohypoparathyroidism (PHP)

    • Pseudo-pseudohypoparathyroidism (PPHP)

IMAGING

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