|Year : 2014 | Volume
| Issue : 3 | Page : 362-365
Uniform hyperdense vessels in non-contrast CT of brain: An unusual finding in plain CT scan diagnostic of polycythemia
Manash Bora, Prabha Kurian, Basavaiya Prabhu Venkatesh, Uppin Shivanna
Department of Radiology, AVMCH, Pondicherry, India
|Date of Web Publication||18-Mar-2014|
Department of Radiology, AVMCH, Pondicherry - 607402
Source of Support: None, Conflict of Interest: None
Polycythemia is a blood disorder in which the proportion of blood occupied by red blood cells increases. It is reflected in raised hematocrit and hemoglobin values. Elevated hematocrit results in characteristic findings of increased attenuation of cerebral vessels and venous sinuses on unenhanced computed tomography. However, these imaging findings can closely mimic those of cerebral venous thrombosis, leading to diagnostic ambiguity. We present a case of polycythemia with typical features of hyperdense cerebral vasculature on non-enhanced computed tomography.
Keywords: Brain, hyperdense vessels, non-contrast computed tomography, polycythemia
|How to cite this article:|
Bora M, Kurian P, Venkatesh BP, Shivanna U. Uniform hyperdense vessels in non-contrast CT of brain: An unusual finding in plain CT scan diagnostic of polycythemia. Med J DY Patil Univ 2014;7:362-5
|How to cite this URL:|
Bora M, Kurian P, Venkatesh BP, Shivanna U. Uniform hyperdense vessels in non-contrast CT of brain: An unusual finding in plain CT scan diagnostic of polycythemia. Med J DY Patil Univ [serial online] 2014 [cited 2017 Sep 26];7:362-5. Available from: http://www.mjdrdypu.org/text.asp?2014/7/3/362/128984
| Introduction|| |
Hyperdense cerebral vessels and venous sinuses on non-contrast computed tomography is a characteristic imaging feature of conditions with raised hematocrit, such as polycythemia. The imaging findings associated with polycythemia have not been well described in literature. Furthermore, its imaging features can mimic cerebral venous sinus thromboses, one of its complications, leading to diagnostic dilemma and warrants further radiological evaluation. We present a case of polycythemia with diffuse hyperdensity of cerebral vasculature and venous sinuses, demonstrating the effect of raised hematocrit in non-enhanced CT (NECT) brain.
| Case Report|| |
A 41-year-old man presented with a history of headache for the past 5 months. There was no significant past history of medical illness or trauma. His clinical examination findings were normal. He was advised NECT brain to rule out any intracranial pathology. All the NECT images of our patient revealed prominent and hyperdense intracerebral arteries and venous sinuses, with HU values ranging from 55 to 70.
These include hyperdense paired vertebral arteries [Figure 1], basilar artery, middle cerebral, anterior cerebral, and posterior cerebral arteries [Figure 2], pericallosal arteries, and sigmoid sinuses [Figure 3].
|Figure 1: Plain axial CT at the level of foramen magnum shows hyperdense paired vertebral arteries (white arrows) with CT density of 61 HU|
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|Figure 2: Plain axial CT at the level of circle of Willis shows hyperdense basilar artery (white arrow), middle cerebral (arrowhead), anterior cerebral (black arrow), and posterior cerebral arteries (curved arrow) with CT densities ranging from 55 to 58 HU|
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|Figure 3: Unenhanced axial CT at the level of midbrain shows hyperdense pericallosal arteries (white arrow) and sigmoid sinuses (arrowheads), with CT densities ranging from 57 to 63 HU|
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The straight sinus, inferior sagittal sinus [Figure 4], vein of Galen [Figure 5], and superior sagittal sinus [Figure 6] were also noted to have abnormally increased density in NECT.
|Figure 4: Unenhanced axial CT at low ventricular level shows hyperdense straight sinus (black arrow) and inferior sagittal sinus (arrowhead) with CT densities of 65 HU and 66 HU, respectively|
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|Figure 5: Plain axial CT at the midventricular level shows hyperdense vein of Galen (white arrow) with CT density of 67 HU|
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|Figure 6: Unenhanced axial CT at the level above lateral ventricles shows hyperdense superior sagittal sinus (curved arrow) with CT density of 69 HU|
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The above findings were suggestive of conditions with raised hematocrit. Further laboratory tests revealed elevated hemoglobin (21 g/dl) and hematocrit (64%), confirming the diagnosis of polycythemia.
| Discussion|| |
Polycythemia, or erythrocytosis, is characterized by an abnormal increase in the number of red blood cells leading to an elevation in hemoglobin concentration and hematocrit (>52% in men and >48% in women). The cause may be primary due to an intrinsic defect in hematopoietic stem cells, secondary due to extrinsic stimulation of progenitor erythroid cells, or pseudopolycythemia in which hematocrit is raised because plasma volume is decreased. Absolute polycythemia, which includes primary and secondary causes, is accompanied by an increased red cell mass and hematocrit values greater than 60% in men and greater than 55% in women. Relative polycythemia is associated with volume loss and contraction and the usual range of hemoglobin and hematocrit in these individuals is between 18 and 20 g/dl and between 49 and 55%, respectively. 
The dominant symptoms from increased red cell mass are related to hyperviscosity and thrombosis (both venous and arterial) because the blood viscosity increases logarithmically at hematocrit values >55%. Neurologic symptoms such as vertigo, tinnitus, headache, and visual disturbances may occur.  Cerebral venous thrombosis is a rare but serious complication of polycythemia.  In our case, the patient's presenting symptom was headache.
The CT attenuation of flowing blood is usually less than 40 HU and is similar to attenuation values of normal adult brain (39 HU); thus, intracranial vessels and venous sinuses appear isodense or mildly hyperdense to adult gray matter on NECT brain.  New et al. demonstrated the linear relationship between CT attenuation values and hematocrit of whole blood preparations. The CT attenuation of hemoglobin was found to be largely due to its protein content, with iron contributing only 7% of the total attenuation.  Ben Salem et al. demonstrated that polycythemia with hematocrit values exceeding 60% will reveal hyperdense cerebral vasculature including circle of Willis and dural venous sinuses in NECT of brain. 
Polycythemia can also present with isolated hyperdense venous sinuses on non-enhanced CT, mimicking cerebral venous thrombosis in patients without thrombosis.  Nelson et al. reported 15 patients with attenuated-appearing dural sinuses on CT without thrombosis; many of them had elevated hemoglobin or hematocrit levels.  The NECT findings in cerebral venous thrombosis include hyperdense thrombus in dural sinuses. The cord sign represents direct visualization of a thrombosed cortical vein that is seen as a linear hyperdensity, which is another finding seen in cerebral venous thrombosis.  Polycythemia is also one of the hypercoaguable states which predisposes to cerebral venous thrombosis. This leads to confusion in the diagnosis of cerebral venous thrombosis in the background of polycythemia. Hyperdense sinuses due to raised hematocrit may be difficult to differentiate from true dural venous thrombosis; but symmetry of involvement, homogeneity of the hyperdensity, and involvement of virtually all visualized dural venous sinuses and major venous structures should suggest that polycythemia is present rather than venous thrombosis,  as was noted in our case.
Further evaluation with diagnostic techniques like magnetic resonance imaging (MRI) and magnetic resonance (MR) venography is preferred when cerebral venous sinus thrombosis is suspected. CT or catheter venography can substitute for MR venography, but MRI is more sensitive than CT in detecting early parenchymal infarction.  Studies by Black et al. have also reported that hemoconcentration correlates with CT attenuation in cerebral venous sinuses. Seven of eight patients with sinus thrombosis had attenuation values >70, but none of the normal subjects had HUs >70. 
Thus, as a case of polycythemia can both mimic and predispose to cerebral vein thrombosis, the indication of NECT in such cases is to help differentiate both these entities and guide the clinician in further evaluation and management of the patient.
Hyperdense vessels can also mimic subdural hemorrhage on an non-enhanced CT, but the symmetry of apparent involvement, the limitation of the hyperdensity in the expected lumen of the dural sinuses, and a negative MRI study would effectively exclude this possibility. 
| Conclusion|| |
The diagnosis of polycythemia is usually made incidentally by laboratory investigations; however, awareness of the characteristic appearance of polycythemia on an non-enhanced CT and its mimics can help avoid misdiagnosis or underdiagnosis of potential complications like cerebral venous thrombosis.
| References|| |
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]