Pseudo-subarachnoid haemorrhage due to chronic hypoxaemia: case report and review of the literature
BMC Neurology
Pseudo-subarachnoid haemorrhage due to chronic hypoxaemia: case report and review of the literature
Maximilian Patzig 0
Christoph Laub 1
Hendrik Janssen 0
Lorenz Ertl 0
Gunther Fesl 0
0 Department of Neuroradiology, University of Munich - Grosshadern Hospital , Marchioninistr. 15, 81377 Munich , Germany
1 Department of Neurology, University of Munich - Grosshadern Hospital , Marchioninistr. 15, 81377 Munich , Germany
Background: The specificity of computed tomography (CT) for subarachnoid haemorrhage (SAH) is very high. However, physicians should be aware of rare false positive findings, also referred to as pseudo-SAH. We present an unusual case in which such a finding was caused by chronic hypoxaemia. Case presentation: A 37-year-old male patient presented with headaches. His CT-scan showed multiple confluent subarachnoid hyperattenuations, which mimicked SAH. However, the headache was chronic and had no features typical for SAH. The patient suffered from severe chronic hypoxaemia due to congenital heart failure. On CT-angiography diffuse intracranial vessel proliferation was found and laboratory results revealed a highly raised level of haematocrit, which had both probably developed as compensatory mechanisms. A combination of these findings explained the subarachnoid hyperdensities. Magnetic resonance imaging (MRI) showed no signs of SAH and visualized hypoxaemia in cerebral veins. A diagnosis of pseudo-SAH was made. The patient's symptoms were likely due to a secondary headache attributed to hypoxia and/or hypercapnia. Therapy was symptomatic. Conclusions: Severe chronic hypoxaemia should be recognised as a rare cause of pseudo-SAH. Clinical evaluation and MRI help differentiate SAH from pseudo-SAH.
Subarachnoid haemorrhage; Hypoxaemia; Hypoxia; Computed tomography; Magnetic resonance imaging
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Background
In the diagnosis of subarachnoid haemorrhage (SAH),
nonenhanced computed tomography (NECT) is known to have
a high sensitivity and an even higher specificity, which has
recently even been reported to be 100% [1]. Thus, false
positive CT findings, sometimes called pseudo-SAH, are
rare. We present an unusual case of pseudo-SAH which
had its origin in chronic hypoxaemia.
Case presentation
A 37-year-old patient had undergone NECT in a
radiological practice because of headaches. The scan showed
bilateral multiple hyperattenuations in the hemispheral sulci
and basal cisterns. A diagnosis of SAH was made and the
patient was referred to our emergency department.
On admission, the patient reported that he had been
suffering from progressively worsening headaches for about
six months. The pain was of a dull, pressing quality and
localized occipitally, radiating to parietal regions
bilaterally. The headache was most severe in the morning
hours, with a maximum of 7 on a pain scale of 010.
Medical history revealed postnatal major cardiac
surgery due to a transposition of the great arteries.
Moreover, several pulmonary embolisms were known and the
patient was on phenprocoumon as a long-term therapy.
On clinical examination, marked cyanosis, clubbed
fingers and hippocratic nails were found, indicating chronic
hypoxaemia (Figure 1). The clinical neurological
examination was negative. Oxygen saturation measured by pulse
oximetry was 70-74%, which the patient said were his
normal values. Laboratory results notably showed a
haematocrit level of 74.8% and a haemoglobin level of
22.1 mg/dl. International Normalized Ratio (INR) was
8.2 and Partial Thromboplastin Time (PTT) was 114 s.
Figure 1 Clinical signs of chronic hypoxaemia. A: Facial cyanosis. B: Clubbed fingers and hippocratic nails.
CT imaging was performed, with the repeated NECT
showing the same findings as the scan performed at the
external radiology practice (Figure 2A). CT-angiography
(CTA) of the intracranial vessels showed no aneurysm
or vascular malformation, but dilated veins ubiquitous in
the subarachnoid space (Figure 2B). The
hyperattenuations on NECT correlated with the course of the vessels
found on CTA. Thoracic CT-angiography revealed atrial
and ventricular septum defects and a pulmonary trunk
fed by both ventricles. The pulmonary arteries were
severely dilated, while the aorta, springing regularly from
the left ventricle, had a small diameter. The right atrium
was enlarged and the right ventricle was hypertrophic.
Severe chronic pulmonary thromboembolism was shown.
As the diagnosis of SAH was now strongly doubted, a
3-Tesla MRI scan (Signa HDx scanner, GE, Milwaukee,
WI, USA) was performed for further clarification. The
protocol included FLAIR, PD and T2*-weighted
sequences as well as susceptibility-weighted angiography
(SWAN) (Figure 2C and D). SWAN revealed the
intracranial veins to be very hypointense and with a large
diameter, due to the susceptibility effect caused by the
increased fraction of deoxyhaemoglobin in the venous
blood of the patient (Figure 2D). The image quality
was markedly reduced because of motion arte (...truncated)