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A “tricky” subarachnoid hemorrhage

SHEA, Yat-fung; TSANG, Hoi-lun Helen; YAP, Yat-hin Desmond; LI, Lai-fung; HO, Wai-shing Wilson

doi: 10.3760/cma.j.issn.0366-6999.20131209

Department of Medicine (Shea YF, Tsang HLH, Yap YHD), Division of Neurosurgery, Department of Surgery (Li LF, HO WSW), Queen Mary Hospital, The University of Hong Kong, Hong Kong, China

Correspondence to: Dr. SHEA Yat-fung, Department of Medicine, Queen Mary Hospital, The University of Hong Kong, 102 Pokfulam Road, Hong Kong, China


(Received May 7, 2013)

Edited by JI Yuan-yuan

To the editor: We report a tricky subarachnoid haemorrhage (SAH). Our patient was a 59-year-old woman with generalized headache for 1 day, which was constricting in nature and rated grade 6/10. Her symptoms were aggravated by lying flat and improved with vomiting. The Glasgow coma scale was full, blood pressure was 142/83 mmHg and pulse 75 beats/min. There was neither neck stiffness nor focal neurological deficit. Fundoscopic examination was normal. She was noted to have hyponatremia (sodium (Na) 122 mmol/L) with serum osmolarity 263 mmol/kg, urine osmolarity 582 mmol/kg, urine Na 117 mmol/L, normal thyroid stimulating hormone and cortisol level. Plain computed tomography (CT) brain was normal (Figure 1A). Lumbar puncture (LP) was performed on day two, and multiple attempts were required. The opening pressure was 15 cmH2O. Blood stained cerebrospinal fluid (CSF) was yielded with serial decrease in redness and interpreted as traumatic tap. Bacterial culture was negative. CSF glucose to blood glucose ratio was 0.5 and CSF protein was 0.77 g/L. Repeated CT brain on day 2 was reported to be normal and her headache improved to 3/10. However, she complained of increased headache (grade 6/10) on day six. CT brain showed SAH at left paraclinoid area and CT angiogram showed an inferior pointing saccular aneurysm 3.5 mm × 6.9 mm × 1.7 mm at supraclinoid segment of left internal carotid artery (ICA) (Figure 1C and 1D). Urgent transarterial coil embolization of aneurysm was performed and her recovery was uneventful. In retrospect, SAH was actually present on second CT brain (Figure 1B). Patient probably suffered from another aneurysmal haemorrhage on day six as suggested by increase headache and more blood at paraclinoid region comparing images on day 2 and day 6 (Figure 1B and 1C).

Figure 1.

Figure 1.

There were several tricky parts precluding early diagnosis of SAH in our patient, including absence of classical thunderclap headache, negative initial CT brain and the difficult LP with misinterpretation of blood stained CSF as traumatic tap. CT brain has been reported to be falsely negative in 7% of aneurysmal SAH.1 Next is to perform LP to look out for xanthochromia or blood stained CSF.2 Unfortunately traumatic tap could occur in 10% of LP performed on urgent basis.3 The classical teaching to differentiate between traumatic tap and SAH is to save CSF in three or four serial tubes. Traumatic tap is likely if there is gradual clearing of redness or red blood cells in serial sampling.3 However this classical teaching was shown to be not reliable and might miss 25% of SAH with negative CT.3,4 Finally the site of SAH is tricky. Paraclinoid SAH is due to ruptured aneurysm in the segment of ICA between the distal dural ring and the origin of posterior communicating artery that is close to the anterior clinoid process.4 Hyperdense signal in this region on CT might be overlooked and mistaken as the partial volume effect from the bony sella and clinoid processes.5 In conclusion, paraclinoid SAH should be carefully looked out in patient with generalized headache with initially “normal” CT brain.

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© 2013 Chinese Medical Association