Clinical Associate Professor Peter Flett, Royal Hobart Hospital (formerly CYWHS, Adelaide), Hobart, Tasmania, Australia. Email: email@example.com
A case of spinal arterio-venous malformation (AVM) initially diagnosed as unilateral cerebral palsy (CP) is reported. The presentation was of a long-standing spastic monoparesis of the left leg, with initial response to Botulinum toxin injections to the calf and tibialis posterior muscles. This was followed by progressive deterioration occurring over a 3-month period before further investigation and definitive diagnosis at 7 years. Imaging demonstrated a large extra-medullary spinal AVM compressing the mid-thoracic cord. This was successfully managed by embolisation with a non-adhesive polymer: ethylene-vinyl alcohol copolymer injected into the dominant feeding vessel. This case highlights the need to consider alternative diagnoses when a child with a diagnosis of CP presents with atypical clinical features such as monoparesis and has worsening or altered clinical signs. Moreover, a normal magnetic resonance imaging brain scan and the absence of ipsilateral upper limb neurological signs or functional impairment should raise suspicion even in the context of static lower limb signs. A literature review was performed on the management of spinal AVM in children and this will be is discussed.
A male child was born by vaginal delivery at term after a normal pregnancy. There were no neonatal complications. Normal developmental milestones were achieved, walking at 14 months of age and speaking in phrases by 2 years of age. An initial diagnosis of left hemiplegic cerebral palsy (CP) was made at 2 years of age by a paediatric neurologist on the basis of lateral circumduction and a toe strike gait pattern affecting the left leg. The left lower limb had signs of an upper motor neurone syndrome, characterised by hyper-reflexia across the knee and ankle, an up-going plantar response and some reduction in muscle bulk of the limb when compared with the non-affected side.
At 5 years of age, examination of the left arm revealed a slight reduction in arm swing when walking, but otherwise there was normal muscle tone, normal deep tendon reflexes and normal function as the non-dominant upper limb. The right arm and leg were normal. Gait was not restricted; however, it was qualitatively non-fluent. The boy, however, became an accomplished break dancer, suggesting normal upper limb co-ordination and muscle strength. Vision and hearing were formally assessed and were normal. He was toilet trained, with no reported bladder or bowel problems. At 5 years, his diagnosis was revised to spastic monoplegic CP affecting only the left lower limb. A magnetic resonance imaging (MRI) of his brain was normal. Neurovasculocutaneous stigmata were not seen.
Over the next 2 years, treatments were required for spasticity and an equinus deformity of the left ankle. This included botulinum toxin A injections to the calf and tibialis posterior muscles and also serial casting with good response. The outcome of these interventions was sufficient to avoid the need for orthopaedic surgical intervention, which had been considered because of concern about spasticity in tibialis posterior and gastrocnemius-soleus complex.
At 7 years, he presented to his paediatric rehabilitation specialist with a very noticeable deterioration of gait, which his family and physiotherapist had noticed steadily getting worse over the preceding 3 months. An examination revealed a change of the previously documented neurological signs with significant weakness in his left quadriceps, hamstrings and tibialis anterior muscles, and obvious foot drop. There was also increased tone in his left calf muscle (gastrocnemius and soleus) and severe spasticity of tibialis posterior. The previously normal right lower limb now showed signs of an upper motor neurone lesion with brisk deep tendon reflexes across the knee and ankle, with a strongly extensor plantar response. There were no cranial nerve abnormalities or upper limb signs. There was no reported back or lower limb pain, no bladder or bowel dysfunction, and no loss of sensation of the lower limbs. On the basis of these new clinical signs, an urgent MRI scan of his spine was performed.
The MRI of the cervical and thoracic spine revealed a large intraspinal vascular mass. This mass was compressing and displacing the thoracic cord between T5 and T7 vertebrae. The mass lesion showed flow void on all sequences. A large feeding intercostal artery arose from the aorta at T10, with a diameter around 50% of the aorta at the same level. A syrinx was noted between C5 and C7 occupying about 60% of the spinal cord diameter. A contrast enhanced computed tomography (CT) scan confirmed these findings (Fig. 1). A unilocular intensely enhancing intraspinal varix was demonstrated (Fig. 2), with thinning and expansion of the pedicles and scalloping of the posterior aspect of the vertebral bodies between T5 and T7, indicating slow expansion of the varix over a period of time.
A neurosurgical opinion determined that surgical intervention was not practical, but because of his progressive neurological signs and rapid loss of ambulatory ability, it was decided that urgent treatment was required and the opinion of an interventional radiologist was sought. The recommendation was for embolisation of the arterio-venous malformation (AVM). Embolisation was performed in two steps. Occluding vascular coils (Gianturco, W.A. Cook, Brisbane, Queensland, Australia) measuring 5 and 8 mm in diameter were placed to reduce inflow. The entire feeding vessel was then occluded using a non-adhesive polymer ethylene-vinyl alcohol copolymer (EVOH) (Micro-therapeutics, San Clemente, CA, USA). After embolisation with these steps, the supplying arterial branch was occluded and fully opacified by the gel (Fig. 3).
Retrosternal chest-pain developed the day after the procedure. A CT scan showed the varix had thrombosed (and has remained so on follow-up). The pain resolved with simple analgesia. No other complications occurred.
Figure 4 shows a late T2 MRI examination showing the varix/malformation with no signal following complete thrombosis. The spinal cord is markedly attenuated immediately above and below this level, and there is also development of a syrinx.
After 1 month, the right leg demonstrated normal power, reflexes and plantar response. After 5 months, lower limb function and clinical signs on the left returned to their pre-existing status. The left lower limb continued to display equinus deformity at the ankle, with spasticity of tibialis posterior and gastrocnemius muscles. Walking continued to be problematic for him as a result of foot drop and limited dorsiflexion in swing; however, his style and symmetry improved with running. Neurological signs have remained stable for 4 years after treatment.
An MRI scan of his spine in 2004 showed a general improvement in appearance of the cord since 2001; however. there was residual less expansile hydro syrinx formation. There was some tethering of the dura posteriorly at the T4-T5 level. The plan was to monitor the boy clinically and to obtain further MRIs later.
1Cerebral palsy with subcategory of spastic monoplegia in the lower limb is extremely rare and should prompt a search for an alternative diagnosis.
2Normal magnetic resonance imaging brain scan and absence of ipsilateral upper limb neurological signs should always raise suspicion of spinal lesions, in this case an arterio-venous malformation (AVM). The late onset of dramatic upper motor neurone signs in the contralateral lower limb excluded the original diagnosis of cerebral palsy.
3Intervention radiology treatment of spinal AVM by embolisation.
Although rare, spinal AVM and other spinal lesions including tumours1 must be considered in the differential diagnosis in children with lower limb spasticity. The exact frequency of spinal AVM has not been determined. They account for between 3 and 11% of all spinal lesions across all ages, although rarer in children.1 In a review of 304 spinal AVMs, only 1.9% occurred in children less than 10 years of age.2 The most common site for a spinal AVM is the lower thoracic spinal cord,1 although they can occur throughout the spinal cord, including the cervical region.3
Prompt diagnosis and early management are keys to preventing long-term sequelae. Therefore, a high index of suspicion is needed to prevent delays in treatment. New and/or progressive neurological signs can be one of various presentations. The typical presentation is slow or sudden onset of progressive impairment of motor function.4 Other symptoms such as intermittent urinary incontinence may be present.4 Alternative presentations include progressive scoliosis or the incidental finding of a spinal bruit.5 Signs consistent with a sub-arachnoid haemorrhage, meningeal irritation or altered conscious state can also occur.6
The optimal management of spinal AVM in both children and adults is unclear. Embolisation is generally recognised as the first stage in treatment,7 the goal is to stabilise the size of the arteriovenous shunt and thus prevent further deterioration. There is some evidence that polymer EVOH would be the embolic material of choice, rather than coils, balloons or particles. However, these studies are retrospective with small numbers.8 Other liquid embolic agents such as n-butyl cyanoacrylate have proved technically difficult to handle.9 The majority of previous published cases describing the use of EVOH for embolisation of a spinal AVM have been in adults.10,11 In the paediatric age group, EVOH has been used successfully to embolise an intramedullary spinal AVM in the cervical spine of an 11-year-old.9 To date, no treatment failures have been reported in the small numbers managed with EVOH.
The role of surgery remains controversial for spinal AVM. A full laminectomy and facetectomy are performed to gain access. In a review of eight adult patients with a dural-based AVM, who underwent surgery following failure of embolisation, no deterioration of symptoms were experienced. Sustained symptomatic improvement for at least 6 months following the procedure was noted.12 Importantly, exacerbation of clinical symptoms has been reported following surgery for AVM.13 Follow-up studies for surgical intervention in children are lacking. The ideal combination of surgical and radiological interventions is yet to be determined. Further treatment options include radiotherapy14 and corticosteroids;15 however, their role in the treatment of this condition is unclear.
Long-term issues potentially remaining for this boy include scoliosis, linear growth restriction, leg length discrepancy, sensory disturbance and cord tethering with progressive upper motor neurone signs involving the lower limbs and urinary and/or bowel incontinence. Re-canalisation with re-occurrence of progressive symptoms and signs is also possible.16 Venous congestion in the spinal vasculature may also precipitate neurological deterioration.17 There are no established guidelines inthe adult or paediatric literature for the follow-up imaging of spinal AVM.
Responsiveness to botulinum toxin type A gave a false confirmation of the previous diagnosis of CP. It is established that the indication for the use of botulinum toxin remains proven for spasticity of cerebral origin18 and now of spinal origin. It was not until the clinical signs had changed so dramatically that investigation leads to a definitive alternate diagnosis. In fact, so rapid was the progression of symptoms that it is the view of the authors that any further delay in diagnosis and treatment could have resulted in paraplegia and permanent loss of ambulation.
Spastic monoplegia is rare, found in less than 5% of the CP population.19 In a review of 217 children with CP, five children with monoplegic CP were identified with four of those children having a specific cause identified.19 In South Australia, of the 230 cases of CP of all types reported to the CP register from 1993 to 1997, only three children (1.3%) were diagnosed with spastic monoplegia.20 Where aetiological factors are not obvious, the diagnosis of (lower limb) monoplegic CP should be made with caution. Spinal imaging should be considered. All health professionals caring for children with CP need to be aware of the natural history of CP so that unexpected changes in clinical features are recognised and investigated appropriately.