Neuroradiology Case of the Week

Case 30

Larry Buadu, MD, PhD, S. Ekholm, MD, PhD, Ramon de Guzman, MD,
Manoj Ketkar, MD, and P-L Westesson, MD, PhD, DDS

Clinical Presentation: Patient is a 12-month-old male with a history of right brachial plexus injury at birth. MRI of the cervical spine was requested as part of preoperative evaluation.

Radiological Findings: Sagittal T1 weighted images through the right neural foramina showed low signal intensity within the C6-7 foramen. The abnormal signal is confirmed on the right parasagittal T2-weighted image (Fig. 1). Showing a rounded area of CSF signal intensity along the lateral margin of the thecal sac. The abnormality is seen to better advantage on the axial T2-weighted image (Fig. 2) through the C6-7 level with CSF signal intensity extending into the right neural foramen, as well as showing a dural margin at the right lateral aspect of the thecal sac.

Figure 1: The abnormal signal is confirmed on the right parasagittal T2-weighted image (arrow).

Figure 2: The abnormality is seen to better advantage on axial T2-weighted images (arrow).

Diagnosis: Pseudomeningocele from traumatic cervical root avulsion.

Discussion: Although MR imaging can define the pseudomeningoceles associated with traumatic root avulsion; myelography and CT myelography remain the gold standard. Nearly 100% of root avulsions have been detected using CT/CT myelography in contrast to MR imaging. Volle et al. [5] found the sensitivities of cervical myelography, CT myelography and MR to be 100%, 45% and 6% respectively, for nerve root avulsions. Evaluation of these patients not only showed level of avulsion but also documented overall size and morphology of the associated pseudomeningoceles. MR imaging has difficulty since pseudomeningocele can occur without a root avulsion, and root avulsions may occur without pseudomeningoceles. High-resolution imaging, potentially with steady state sequences and three-dimensional imaging, may allow evaluation of exiting and entering rootlets and more specifically define sites of avulsion.

References:

1. Caravalho GA, Nikkhah G, Matthies C, et al. Diagnosis of root avulsions in traumatic brachial plexus injuries: value of computerized tomography myelography and magnetic resonance imaging. J Neurosurg 1997;86:69-76
2. Gasparotti R, Ferraresi S, Pinelli L et al. Three dimensional MR myelography of traumatic injuries of the brachial plexus. Am. J Neuroradiol. 1997; 18: 1733-1742.
3. Hashimoto T, Mitomoto M, Hirabuki N, et al. Nerve root avulsion of birth palsy: comparison of myelography with CT myelography and somatosensory evoked potential. Radiology. 1991 Mar;178(3):841-5.
4. Hayashi N, YamamotoS, Okubo T, et al. Avulsion injury of cervical nerve roots: enhanced intradural nerve roots at MR imaging. Radiology 1998;206:817-822.
5. Volle E, Assheuer J, Hedd J, et al. Radicular avulsion resulting from spinal injury: assessment of diagnostic modalities. Neuroradiology 1992;34:235.