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A 41-year-old man presented with a sudden onset severe occipital headache, vomiting, neck stiffness and photophobia. He had been previously well, aside from chronic mid and lower back pain. There was no focal neurological deficit and a plain CT head scan was normal. Subsequent lumbar puncture (LP) was heavily bloodstained with analysis showing sequential increase in red blood cell count (144 000×106/L first tube and 225 000×106/L third tube). It was not possible to undertake testing for xanthochromia as the cerebrospinal fluid (CSF) supernatant was grossly haemolysed. We prescribed nimodipine for presumed intracranial subarachnoid haemorrhage. CT angiogram and a digital subtraction cerebral angiogram showed no intracranial vascular abnormality. His symptoms improved and we made a putative diagnosis of benign thunderclap headache. At this point, we attributed the bloodstained CSF to traumatic LP and he was discharged with analgesia and neurology follow-up.
Three weeks later he developed a 1-week history of new lumbar back pain, numbness of the sacrum and penis, shooting pains in the lower limbs, progressive constipation, involuntary flatus and urinary urgency. On readmission, he had lower limb weakness, brisk knee and ankle jerks and flexor plantar responses. He had a sensory level to pin prick at T12. His bladder was palpable with a postmicturition residual volume of 750 ml.
T2 weighted MRI spine showed oedema within the lower cord extending to the conus. There were multiple aberrant flow voids within the spinal canal, including a nest of abnormal vessels closely associated with the conus. The appearance suggested an arteriovenous malformation (figure 1).
Selective spinal angiogram demonstrated an arteriovenous fistula. A prominent L1 radicular-medullary artery supplied an ectatic inferior portion of the anterior spinal artery, which in turn directly supplied the fistulous point on the anterior surface of the conus (figure 1, right panel).
The patient underwent neurosurgical correction under angiographic guidance. The fistula was located on the anterior spinal artery among multiple dilated vessels, and so correct placement of the occluding clip was clearly critical. Therefore surgery was performed in the vascular theatre with on-table angiography. The radicular vessel was cannulated, the cord then exposed and gently rotated to place a temporary clip. Angiography showed the clip was proximally placed, so this was replaced and confirmed to be correct with further angiography prior to final occlusion.
One month postoperatively, he required a wheelchair to mobilise and had ongoing sensory disturbance in his lower limbs, urinary urgency and constipation. By 6 months his function had improved, walking for short distances with a frame and requiring a wheelchair outside his home. His bladder has remained neuropathic with little improvement in lower limb sensation.
Arteriovenous malformations are aberrations of vascular anatomy with abnormal connections arising between the veins and arteries. Increased pressure within the venous system results in tortuosity of the vessels and venous hypertension.1 Lumbar arteriovenous malformations may be congenital or acquired, such as following trauma. The presentation is usually insidious with back pain and progressive myelopathy, giving leg weakness and sensory disturbance. There is often bladder and bowel dysfunction.2 A minority of cases have a rapid onset and deterioration of symptoms known as subacute necrotising myelopathy (Foix–Alajouanine syndrome) with pathological findings of spinal cord necrosis.3 Sudden onset headache and other symptoms of subarachnoid haemorrhage are rare and mostly occur with cervical rather than lumbar arteriovenous malformations.4–9
In this case, the headache that prompted initial presentation was severe and associated with signs of meningism. It may have represented bleed from the malformation, similar to that associated with intracranial aneurysms. However, another possibility is that the original presentation was a benign headache and the LP itself provoked a decompensation in pressure in the intrathecal system, which later produced a myelopathy. The original presentation with a purely occipital headache without back pain might support this possibility. Decompensation of arteriovenous malformations following LP can occur, whereby reduced intrathecal pressure interrupts blood flow dynamics within the malformation to accentuate cord ischaemia.3 There is also the possibility of direct trauma to the arteriovenous malformation or associated engorged vasculature.
Spinal MRI and angiography are the primary imaging modalities for arteriovenous malformations.10 MRI may show perimedullary vein enlargement, flow voids and cord oedema. There may be T2 signal change within the cord, although it is not of prognostic value.11 ,10 Angiography can highlight early venous filling and congestion of tortuous dilated veins and provide more detailed information about the location of the shunt.
Our patient underwent cord imaging after developing a myelopathy, 3 weeks after his initial presentation. This 3-week delay is much shorter than the average time to diagnosis of 11–18 months reported in the literature.10 ,12 However, given the initial bloodstained cerebrospinal fluid, should things have been done differently at his initial presentation? Most would agree that with a negative intracranial angiogram and features suggesting a traumatic LP, no further imaging was needed at that point; it was not until new lower limb symptoms developed that spinal imaging was required.13 However, this case highlights the very important lesson that bloodstained cerebrospinal fluid should not necessarily be dismissed as traumatic in the presence of a normal intracranial angiogram; rather, the clinician should consider the possibility that the blood originated from a spinal source; if there are clinical clues to support this, the patient should have spinal imaging. The ‘three-tube test’, that looks for a falling cell count in consecutive CSF samples, does not reliably differentiate a traumatic tap from subarachnoid haemorrhage.13 ,14 Furthermore, particularly bloodstained CSF contains increased oxyhaemoglobin, which interferes with CSF bilirubin detection and is a confounding element in interpretation.15
Delay in diagnosis often results from initial incorrect diagnoses, including spinal stenosis, demyelination, spinal cord tumours or peripheral nerve disorder.2 ,10 In spite of this, there are several reports of a favourable outcome in patients after significant diagnostic delay and accordingly these lesions should be treated regardless of prolonged symptom duration or pronounced neurological deficit.12
Spinal arteriovenous malformations are rare pathological entities that may mimic cerebral aneursymal subarachnoid haemorrhage. Patients with a convincing history of subarachnoid haemorrhage but negative cerebral angiography, especially in those with blood in the CSF, with clinical features of a myelopathy, or new limb symptoms following LP, should undergo detailed spinal imaging.
Dr Samuel P Walker for editing figure 1.
Contributors SN, SM and RSW prepared the initial manuscript. Imaging (figure 1), legend and references within the body to the radiological procedure were provided by PC. ND reviewed and edited aspects related to the neurosurgical management of the case. DM reviewed and edited aspects related to the neurological assessment and management within the case.
Competing interests None.
Provenance and peer review Not commissioned. Externally peer reviewed. This paper was reviewed by Richard Davenport, Edinburgh, UK.