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Q1: What differential clinical diagnoses would you consider?
The differential diagnoses include:
Infective—for example, tuberculosis of the spinal cord, tertiary syphilis.
Vascular—for example, anterior spinal artery thrombosis, embolic phenomena (for example, subacute infective endocarditis), sagittal sinus thrombosis.
Q2: What do the spinal MRI scans show (see p 472)?
The scans show swelling of the spinal cord from the middle thoracic region to the conus medullaris. The margin of the spinal cord is unclear with intramedullary increased signal intensity and the spinal canal seems to be occupied mostly by the swollen cord.
Q3: What was the first treatment given which was followed by paraplegia?
The patient was started on intravenous methylprednisolone infusion (1 g daily) for presumed inflammatory myelitis/vasculitis. On the third day and after two infusions, he lost bladder sensation and knee jerks, and became paraplegic. The steroids were stopped. In our experience this is the second patient with a similar presentation who developed paraplegia after intravenous steroids.
Q4: What is the pathological abnormality suggested by the spinal angiogram (see p 472)?
The spinal angiogram shows an arteriovenous fistula fed from the left T5 intercostal artery.
Q5: What specific treatment did the patient receive?
The vessel was catheterised and its feeder (the fistula) was blocked with coils and glue.
Spinal arteriovenous malformations (AVMs) are rare. The majority are radiculomeningeal,1 also known as spinal dural arteriovenous fistulas.2 The condition is thought to be caused by venous hypertensive congestion of the spinal cord caused by dysfunction of the “draining” nearby dural nidus.
There are no pathognomonic clinical features and the diagnosis may be difficult unless there is a high degree of clinical suspicion. Even in younger patients treatable causes of paraplegia are often diagnosed late with tragic results.3
In a review of 55 cases, AVMs were more common in males (7:1) with an average age of presentation at 57 years. The most common symptom was weakness of the legs (95%), accompanying impairment of bladder function (89%), and impairment of bowel control (85%). Most patients had a combination of motor, sensory, and sphincter disturbance. The clinical course was progressive in most patients (78%) and acute in onset in 11% of patients. The duration of symptoms was less than three years in 66% of patients and less than one year in 10% of patients.4
Our patient did not have signs of infection or malignancy, but he did have radiological features of ischaemic/necrotic spinal cord which would explain the rising inflammatory markers as his symptoms progressed.
The development of selective spinal angiography in the early 1960s has enabled better evaluation and classification of AVMs. An analysis of 240 spinal angiograms in 132 patients revealed 97 AVMs that included 66 spinal dural AVFs. The nidus of the fistula was located between T6 and T12 in 61%, in the sacrum in 9%, and intracranially in 8% of cases.5
The advantages of MRI in demonstrating intramedullary malformation are multiplanar imaging, high soft tissue contrast, and absence of ionising radiation.
Successful management depends on early suspicion of the diagnosis and confirmation of the disorder and a clear understanding of the lesion's anatomical location as early treatment may only slow the progression of the disease rather than reversing symptoms or acquired deficits.
Treatments of AVMs include surgery, embolisation, or both. Endovascular treatment is less invasive, causes less morbidity, and may ensure earlier recovery. If embolisation has failed, surgery can still be an option.
Morgan and Marsh described recanalisation in 11 of 18 embolisation treatments in 14 patients using polyvinyl alcohol with recurrence of symptoms.6 In a recent report of 18 patients Mareyet al recommend thatN-butyl-cyanoacrylate embolisation be the initial treatment of choice for arteriovenous fistulas with venous drainage.7 Patients should be followed up closely with periodic clinical and radiological assessments. MRI and spinal angiography are essential to achieve the best clinical benefit and possible cure.
Spinal dural arteriovenous fistula.
Spinal AVMs are rare disorders that should be added to the list of causes of progressive leg weakness in middle aged and elderly patients.
It is associated with considerable difficulty in diagnosis which can lead to treatment delay in most patients.
Successful treatment requires early diagnosis and the correct understanding of the anatomy of the lesion and its angioarchitecture and the limitations of both surgery and endovascular embolisation.