Conus Abnormality



Conus Abnormality


Bryson Borg, MD



DIFFERENTIAL DIAGNOSIS


Common



  • Filum Terminale Fibrolipoma


  • Primary Cord Neoplasm



    • Ependymoma, Myxopapillary, Spinal Cord


    • Astrocytoma, Spinal Cord


    • Hemangioblastoma, Spinal Cord


    • Paraganglioma


  • Demyelinating Disease


  • Syringomyelia


  • Tethered Spinal Cord


Less Common



  • Cavernous Malformation, Spinal Cord


  • Infarction, Spinal Cord


  • Ventriculus Terminalis


Rare but Important



  • Metastases, Spinal Cord


  • Arteriovenous Malformation/Fistula


  • Developmental Abnormality



    • Terminal Lipoma


    • Diastematomyelia


    • Dorsal Dysraphism



      • Myelomeningocele/Myelocele


      • Lipomyelomeningocele/Lipomyelocele


      • Terminal Myelocystocele


    • Caudal Regression Syndrome


    • Segmental Spinal Dysgenesis


  • Infection



    • Schistosomiasis


    • Cysticercosis


    • Tuberculoma


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • MR without and with contrast is the best tool to evaluate conus and spinal canal


Helpful Clues for Common Diagnoses



  • Filum Terminale Fibrolipoma



    • Fat within otherwise normal filum terminale, anywhere between conus and sacrum


    • No tethering, asymptomatic; incidental finding in 4-6%


  • Primary Cord Neoplasm



    • Ependymoma, Myxopapillary, Spinal Cord



      • Most common neoplasm of conus and lumbar canal


      • Marked enhancement typical


      • Can show signs of necrosis (heterogeneity, cyst formation) and hemorrhage: Subarachnoid hemorrhage, superficial siderosis


      • Bony remodeling when large: Vertebral scalloping, foraminal enlargement, widened and eroded pedicles


    • Astrocytoma, Spinal Cord



      • Cervical/upper thoracic most common; rarely involves conus


    • Hemangioblastoma, Spinal Cord



      • Focal hyperenhancing lesion(s), often with disproportionately large syrinx


      • Multiple sites of involvement in cord and posterior fossa typical


      • Often with signs of prior hemorrhage


      • 70-90% NOT associated with von Hippel-Lindau


    • Paraganglioma



      • Virtually indistinguishable from the much more common myxopapillary ependymoma


    • Infection (e.g., schistosomiasis) can simulate a conus neoplasm


  • Demyelinating Disease



    • Isolated involvement of the conus with multiple sclerosis probably extremely rare


    • Case reports of isolated conus involvement with other causes of demyelination (e.g., ADEM)


  • Syringomyelia



    • Hydrosyringomyelia of the conus can occur as an isolated finding or as a component of more extensive involvement


    • Terminal syringomyelia can be seen with tethered cord


  • Tethered Spinal Cord



    • Tip of conus usually lies at the T12-L2 level


    • Tip of conus below L2-3 is abnormal


    • Associated abnormalities include thick filum, dysraphism, vertebral anomalies, etc.


Helpful Clues for Less Common Diagnoses



  • Cavernous Malformation, Spinal Cord



    • Variable hyperintensity on T1, heterogeneously hyperintense on T2 with surrounding rim of susceptibility due to prior episodes of hemorrhage, which blooms on gradient echo sequences



    • Rare enhancement; may have some surrounding edema if recent bleed


  • Infarction, Spinal Cord



    • Hyperintensity on T2WI, possibly with mild expansion


    • Most often associated with aortic pathology (dissection, thoracoabdominal aortic surgery), rarely with atherosclerotic disease or embolism


  • Ventricularis Terminalis



    • Incidental, transient finding of childhood mild dilatation of the caudal terminus of the central canal in an otherwise normal conus


    • Up to 2-4 mm diameter and ≤ 2 cm length


    • No signal changes or enhancement in adjacent parenchyma


Helpful Clues for Rare Diagnoses

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Aug 7, 2016 | Posted by in NEUROLOGY | Comments Off on Conus Abnormality

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