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Traumatic upper limb weakness in a man with type 1 neurofibromatosis
  1. Esther Shu-Ting Ng1,
  2. Cheng Kang Ong2,
  3. Einar Wilder-Smith1
  1. 1Department of Medicine, National University Singapore, Singapore
  2. 2Department of Diagnostic Imaging, National University Health System, Singapore
  1. Correspondence to Professor Einar Wilder Smith, Spinal Injury Centre, Universitaetsklinikum Heidelberg, D-69118 Heidelberg, Germany; mdcwse{at}nus.edu.sg

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A 37-year-old right-handed man presented with left arm weakness 4 months after a shoulder trauma, which was caused by somebody landing on him while swimming. There was initial left upper limb numbness and neck pain radiating to the left back with subsequent weakness of shoulder movement. He had type 1 neurofibromatosis (NF-1) with skin manifestations but no known neurological complication.

On examination, power of shoulder abduction, flexion and extension and elbow flexion on the left was 2 (Medical Research Council grade), shoulder elevation was 4+ and there was moderate scapular winging. Power of all other muscle groups was 5. Left biceps and triceps reflexes were decreased. Sensation was normal as was the rest of the neurological examination.

Nerve conduction studies showed abnormality of myotomes supplied by C5, C6 and, to a lesser degree, C7, while electromyography showed evidence of active and chronic denervation.

The patient underwent ultrasound of the neck and MRI of the cervical spine. Ultrasound showed a large irregular area of abnormal and increased blood flow at the C5 root. There was thickening of nerve roots on the left, with surface areas of 0.13, 0.24 and 0.17 cm2, respectively, for C5, C6 and C7, measured using ultrasound. The right C5, C6 and C7 measured 0.10, 0.18 and 0.12 cm2, respectively, and were within the normal laboratory values. MRI revealed marked posterior scalloping of the lower four cervical vertebral bodies (figure 1).

Figure 1

Sagittal T2-weighted magnetic resonance image of the cervical spine showing posterior scalloping of the lower four cervical vertebral bodies (arrow).

The patient underwent CT angiogram (figure 2) and a digital subtraction angiogram (figure 3), which demonstrated a cervical extradural arteriovenous fistula (AVF) fed by the left vertebral artery within the left C4 foramen transversus. The venous drainage was exclusively epidural, with no dural or intramedullary venous component. The markedly distended epidural veins encroached upon and displaced the spinal cord.

Figure 2

CT angiogram showing (A) left vertebral artery (arrow) surrounded by an enlarged venous sac just proximal to the fistula and (B) exact point of the fistula where a direct communication is seen between the vertebral artery and the adjacent venous system (arrow).

Figure 3

Digital subtraction angiography showing (A) exact arteriovenous fistular communication (arrow) of the vertebral artery surrounded by the enlarged venous sac and (B) engorged epidural venous system with eventual drainage through the left vertebral vein.

In AVFs associated with NF-1, there are two possible mechanisms by which an AVF may arise.1 First, dysplastic smooth muscle or neurofibromatosis proliferation in the vessel wall may lead to vasculopathy, aneurysm formation, leakage and ultimate rupture into adjacent veins. It is notable, however, that there is no evidence for the association between NF-1 and intracranial aneurysms.2 The second possibility would be that the arteriovenous malformation arises congenitally as a manifestation of mesodermal dysplasia.

In our patient, it is possible that the fistula and adjacent veins were initially small, but enlarged secondary to tissue disruption with the neck trauma, leading to expansion and compression of the nerves. This has been reported by Kāhārā et al3 in a patient who developed symptoms following trauma; the patient developed numbness and radiating pain in the upper limb, followed by weakness, similar to our patient.

Diagnosis of spinal AVF can be established by MR imaging, angiography or CT. Spinal AVF in NF-1 patients may be confused with the common dural spinal AVF as classified by Kendall and Logue.4 In the latter, the fistula is between a radicular artery and a vein at the dural root sleeve with intradural spinal cord venous drainage. In distinction, AVFs in NF-1 are epidural and expand into the paraspinal space, where they result in nerve compression, rather than draining directly into the spinal cord venous system.5 The goal in managing AVFs in NF-1 is the complete occlusion of the fistula, either by surgical or by endovascular treatment.

References

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Footnotes

  • Competing interests None.

  • Patient consent Obtained.

  • Provenance and peer review Not commissioned; externally peer reviewed.