In this overview we present 15 cases of different pathologies found in medullary conus or cauda equina, including ischemia, inflammatory changes, tumors and postsurgical complications, with their typical radiological presentation.

Congenital diseases may present perinatally, but also later in life due to occult manifestation or insidious clinical course.

Fig 1: MRI of a patient with neurofibromatosis type 2. (1a) and (1c) T1W postcontrast images demonstrate multiple enhancing nodular lesions along the cauda equina roots, (1b) T2W image shows isointensity of nodule. Findings are consistent with peripheral nerve sheath tumors.

Degenerative processes are common in the spine due to its complex anatomical structure, with each component susceptible to degeneration. A herniated lumbar intervertebral disc is the most common cause of compression in cauda equina syndrome.

Fig 2: MRI of a patient with multiple comorbidities and high operative risk. T2W sagittal (2a) and axial (2b) demonstrate severe spinal canal stenosis caused by intervertebral disc protrusion and prominent juxtacortical synovial cyst next to the left facet joint (orange arrow). Intradural CSF is obliterated with compression of cauda equina roots (blue arrow), with some roots still separated from each other.

Demyelinating diseases are characterized by inflammatory demyelination and lead to progressive motor and sensory impairment, leading to significant disability over time. Spinal cord demyelinating lesions present as T2W hyperintense focal or diffuse lesions. They can lead to axonal loss and spinal cord atrophy. Their enhancement occurs less frequently than in the brain and is typically subtle.

Fig 3: MRI of a patient with RRMS. (3a) and (3b): T2W images reveal a demyelinating lesion in the hypotrophic medullary cone (yellow arrow), with no enhancement on T1W postcontrast images (3c, d). An incidental finding (red arrow) shows an intradural, extramedullary nodule with intense enhancement, corresponding to a small schwannoma.

Ischemic injury typically leads to abrupt onset of neurologic deficits due to vascular compromise, but fortunately is rare due to extensive anastomotic blood supply of medulla. In acute phase MRI demonstrates a high T2 signal within the cord, the pattern of which depends on the territory. Most cases involve the anterior spinal artery, with characteristic the "owl-eyes sign” (also known as the “snake-eyes or fried-eggs sign”) seen on axial T2W MRI images. This represents symmetric high T2W signal foci in the anterior horn cells of the spinal cord. Cord expansion is non-specific finding which may often be seen in ischemia, but also in tumors and inflammation. DWI is problem solving sequence, which, although technically challenging to implement in spine, still can reliaby confirm ischemic nature of the lesion by demonstrating restricted diffusion.

Fig 4: MRI of a postpartum patient with bilateral pulmonary embolism and acute onset of paraplegia. (4a) and (4b): Sagittal T2W images show central intramedullary hyperintensity (yellow arrows). (4c) and (4d): DWI images show restricted diffusion in the corresponding area of the spinal cord (blue arrows). There was no contrast enhancement (not shown). Findings are indicative of acute ischemia.

Infectious and inflammatory processes may be linked to autoimmune disorders or may be of infective nature (bacterial, viral, fungal or parasitic). Bacterial infection can present as meningitis, epidural abscess, myelitis, or as a rare entity of spinal cord abscess. An intramedullary abscess presents as a central T2 hyperintensity with a hypointense rim, accompanied by cord edema and ring or peripheral enhancement. Viral and fungal spinal cord infections are seen in immunocompromised patients, with often non-specific imaging findings of intramedullary T2 hyperintensity. Parasitic myelitis is rare, the most common culprits are toxoplasmosis and cysticercosis, with usually simultaneously present brain lesions. On MRI they present with extensive cord edema and enhancing intramedullar lesions.

Fig 5: MRI of a three-year-old patient with suspected viral encephalitis, (5a) and (5b): T2W images showed edema and enlargement of the medullary cone (yellow arrow), (5c): T1W postcontrast image showed no enhancement (red arrow). Considering the clinical context, findings were consistent with inflammation–myelitis.

Fig 6: MRI of the whole spine in a patient with RRMS and acute deterioration, progressing from flaccid paraparesis to tetraparesis and respiratory insufficiency, unresponsive to corticosteroids and myasthenia gravis treatment. T1W sagittal images pre- (6a) and postcontrast (6b-d) reveal confluent cervical spinal cord enhancement, discontinuous thoracic cord enhancement, and partially nodular enhancement along the medullary cone surface (blue arrows). Differential diagnoses included sarcoidosis, other granulomatous inflammation or carcinomatosis. In further work-up FDG PET-CT showed no signs of carcinoma. Sarcoidosis was excluded by a wide clinical work-up. Final diagnosis was antiGAD encephalomyelitis.

Fig 7: MRI of a patient with a two-week history of progressive ascending lower extremities weakness and sensory deficits. (7a) T2W sagittal shows no cone or clearly visible cauda roots abnormalities. L4/L5 disc pseudobulging (white arrow), with no acute clinical significance. Postcontrast T1W sagittal (7b) and axial (7c,d) images reveal cauda equina root enhancement, considering clinical presentation such imaging pattern is typical for acute polyradiculoneuritis.

Guillain-Barré syndrome includes a spectrum of autoimmune polyradiculopathies affecting motor, sensory, and autonomic nerves. Imaging aids in unclear cases and differential diagnosis. Post-contrast studies are crucial, as non-contrast sequences, as in our case, are often normal. Typical findings include spinal nerve root thickening and enhancement.

Neoplasms, either primary or metastatic spinal cord tumors, exert mass effect that contributes to neurological deterioration through compression or infiltration of the neural structures. Primary intramedullary tumors such as ependymomas and astrocytomas may arise within the conus, while extramedullary intradural tumors such as meningiomas and schwannomas may cause external compression.

Fig 8: MRI of a patient with a history of sensory deficit and left leg pain (8a) sagittal T2W image shows a heterogeneous intramedullary mass in the medullary cone (red arrow), with a proximal syrinx (blue arrow). (8b) T1W postcontrast image reveals avid enhancement of the lesion. Morphologically similar lesion is visible in the sacral spinal canal (yellow arrow), and a small nodule among cauda equina roots. Postsurgical pathology diagnosis was myxopapillary ependymoma (WHO grade 2) with drop metastases at the end of the dural sac and along the cauda equina roots (orange arrow).

Fig 9: A 36-year-old patient with a history of Ewing’s sarcoma of the foot presented to the emergency department with conus medullaris syndrome. MRI showed: (9a) intradural extramedullary mass compressing the cone (yellow arrow). Mass was pathologically confirmed as Ewing sarcoma metastasis. Postoperative MRI (9b) T2W and (9c) postcontrast T1W performed 2 months after surgery showed local recurrence of the tumor (red and blue arrows), with new multiple bone metastases (yellow arrows).

Fig 10: MRI of a patient with a history of mantle cell lymphoma and autologous hematopoietic stem cell transplantation, who presented with cauda equina syndrome preceded by 12-months-long lower back pain (10a) T2W images show multiple intradural fusiform hypointense masses inseparable from the cauda equina roots.

Fig 11: (10b) Sagittal STIR image depicts infiltrative mass around the medullary cone (yellow arrow), (10c) and (10d) T1W postcontrast images show intense homogeneous enhancement of the mass (blue arrow), with enhancement of the enlarged spinal nerve roots (red arrow). Findings are indicative of intradural lymphoma with infiltration of cauda equina and extradural infiltration of spinal nerves.

Traumatic injuries to the conus medullaris and cauda equina can be caused by displaced vertebral fractures, disc herniations and penetrating injuries. Clinical suspicion of such injuries should be raised if a patient develops neurological deficits, which then requires MRI to clarify the nature of the injury.

Fig 13: MRI of a patient with prior trauma and lower back pain shows a recent L4 vertebral body fracture (red arrow) with extensive edema (12a,b) and post-contrast enhancement (12c). No evidence of injury of medullary cone or cauda equine nerves. There is linear lipoma of the filum terminale (12b and d, blue arrow), a common incidental finding with no clinical significance.

Postoperative complications of spinal cord surgery can be early, appearing in the perioperative period. Early complications include hemorrhage, CSF leak and infection. Symptoms of cord or cauda equina compression in the early postoperative period should raise suspicion of an epidural hematoma. CSF leak is rare, but can result in the formation of pseudomeningocele, CSF cutaneous fistula and intracranial hypotension. Late complications include scarring, adhesions, and persistent neural compression, which may contribute to delayed neurological recovery.

Fig 14: MRI of a patient with previous reduction of the epidermoid cyst of the medullary cone, who presented with increasing difficulty in walking and deteriorating sphincter control. Preoperative (13a) sagittal T1W and (13b) axial T2W images show heterogeneous intradural mass containing fat, which was compressing the cone (yellow arrow), consistent with a recurrent epidermoid cyst. Postsurgical MRI (13c) and (13e) T2W images and (13d) T1W reveal intradural (blue arrow) and intramedullary (green arrow) hematomas mildly compressing the cone and cauda equina roots. The red arrow indicates hemostatic material.

Fig 15: MRI of a patient hospitalized for a fever of unknown origin. During hospitalization, the patient developed cauda equina syndrome and was referred for an emergency MRI. Sagittal T2W (14a), T1W (14b), and post-contrast T1W (14c) images reveal an intradural hemorrhagic mass (red arrow) with moderate enhancement (white arrow). Multiple bone metastases were also observed, with some visible in these images (orange arrow). Pathological diagnosis was hemorrhagic metastasis of a carcinoma of unknown primary origin with undifferentiated anaplastic cells.

Fig 16: Postoperative MRI of a patient who presented several days after microdiscectomy with fever, poor general condition, and signs of wound infection. Sagittal STIR (15a) shows a subcutaneous inflammatory collection with gas locules (green arrow) and surrounding soft tissue edema. Postcontrast T1W axial images (15b and c) show intense enhancement of tissues around the collection (blue arrow) and enhancement of cauda equina roots at the level of the surgical site (red arrow), consistent with meningitis. The second surgery proved purulent wound infection and meningitis.