Sex: male
Age: 67 years
History
The patient has a history of primary myelofibrosis confirmed by bone marrow examination.
Laboratory data
Serum laboratory findings revealed the following abnormal findings: hemoglobin 5.7 g/dl; erythrocytes 2 x 103/mm3; hematocrit 17.5%, leukocytes 5.6 x 109/liter. Liver and renal functions tests were normal.
Physical findings
Physical examination showed a pale and cachectic man. The spleen was enlarged without hepatomegaly. Formal neurological examination showed diminished power, exaggerated deep tendon reflexes, and bilateral ankle clonus. A sensory level is detected at the mid-thoracic region (T12). There was no functional urinary disturbance.
Case text
The patient was admitted due to progressive sensory loss of both lower extremities and increasing pain on both feet. No radicular pain was present.
Image 1-4
MR imaging of the cervico-thoracic spine
(1) Sagittal T1-weighted image; (2) sagittal T2-weighted image; (3,4) sagittal (3) and axial (4) contrast-enhanced T1-weighted images. Axial image was performed at T10 intervertebral level.
Image 5-6
CT of the chest
(5,6) Axial images displayed at bone (5) amd soft tissue window (6).
Image 1-4
1. Describe the imaging findings.
An large posterior epidural mass extending from C5 to T12 level with compression of the spinal cord, especially at the midthoracic level is noted. In addition, transverse images reveal a paravertebral mass the T-10 level extending into the spinal canal through the neuroforamen. The epidural mass is slightly hyperintense on T2-weighted images and shows homogenous contrast enhancement.
2. What are the signal characteristics of the vertebral bone marrow?
The marrow is of low signal intensity on both T1- und T2-weighted sequences. This finding is consistent with marrow replacement in myelofibrosis.
3. What is your next diagnostic step?
Needle biopsy of the thoracic paravertebral mass.
Image 5-6
4. What are the imaging findings on the CT scan?
The CT scan demonstrates a bilateral paravertebral soft-tissue mass.
5. What is your differential diagnosis in this case?
Extramedullary hematopoiesis, epidural infection, lymphoma or metastasis with epidural manifestation.
6. Given the history of myelofibrosis and the imaging findings what is the most likely diagnosis of this case?
Extramedullary hematopoiesis.
Final diagnosis
Extramedullary hematopoiesis with spinal cord compression in a patient with myelofibrosis.
Differential diagnosis
Epidural infection, lymphoma or metastasis with epidural manifestation.
Discussion
During intrauterine development, marrow growth is both skeletal and extraskeletal. At birth, hematopoiesis is exclusively skeletal. Formation of apparently normal marrow outside the skeleton sometimes recurs, even during adult life. Extramedullary hematopoiesis is a well known complication of many chronic hematological disorders inclcuding thalassaemia, sickle cell anemia, myeloproliferative disorders, and myelofibrosis. The most common localizations of extramedullary hematopoiesis are the liver and spleen. The kidneys, mediastinum, pericardium, adrenal glands, and sclera are less commonly involved. Extramedullary hematopoiesis with involvement of the dura mater of the spinal cord is rather uncommon. The exact origin of extramedullary hematopoiesis is unknown, but the dura mater has hematopoietic capacity in the fetus and it may therefore develop from primitive rests. An alternative explanation is the embolization of hematopoietic stem cells to the dura mater. However, it seems unlikely that extramedullary hematopoiesis arisis from extrusion of vertebra bone marrow in the absence of bony erosions or fractures.
Spinal cord compression secondary to extramedullary hematopoiesis is commonly localised in the mid-lower thoracic region.
When presenting as an epidural mass, extramedullary hematopoiesis has to be differentiated from other causes of epidural masses including metastasis, infection, and lymphoma.
Although biopsy remains the gold standard MR imaging has an important role in narrowing the differential diagnosis and in tailoring adequate treatment. In addition, MR imaging has shown to be useful in the follow-up after radiotherapy of epidural involvement of extramedullary hematopoiesis.