A 38-year-old woman presented with lumbar pain that had increased during the past weeks especially with movements and decreased with bed resting. This pain radiated to the right lower limb and was associated with paraesthesias and disaesthesias.
The physical and neurological examination showed no abnormalities.
MRI was performed and showed a 13 mm predominantly cystic expansile lesion with a thick wall that showed marked rim enhancement. The location was difficult to establish if it was extramedullary with intramedullary invasion or intramedullary with extramedullary invasion. The lesion was associated with significant cord oedema inferiorly and superiorly.
The patient underwent surgery, where the diagnosis was made.
Spinal MRI is the best technique for the evaluation of spinal cord lesions, which allows to locate it intramedullary or intradural extramedullary, narrowing the differential diagnosis. The difficulty of this case was first to distinguish if the lesion was intra, extramedullary or combined. Second, the rim enhancement with marked secondary intramedullary oedema was difficult to match with tumoral or cystic lesions.
The most important criteria to distinguish intramedullary neoplasms from non-neoplastic spinal cord lesions are cord expansion, lesion enhancement and associated cysts.
Intramedullary neoplasms usually show at least some degree of enhancement, in fact, the lack of enhancement is the primary imaging feature to differentiate this kind of neoplasms from other noneoplastic tumour-like conditions [1, 2].
Cystic tumoral lesions include cystic astrocytoma and ependymoma as the most common lesions, but also haemangioblastoma, ganglioneuroma or cystic meningioma, therefore this is not specific. Ependymoma is the most common intramedullary spinal tumour in adults; the myxopapillary variant is typically located in the conus medullaris and filum terminale [2, 3]. Both astrocytomas and ependymomas are generally associated with cord oedema and enlargement.
On the other hand, we must consider in our differential diagnosis some non-neoplastic spinal cord lesions such as epidermoid cyst or granulomatous diseases. Epidermoid cyst shows thin enhancement and is not associated with cord oedema. Granulomatous diseases, mainly TB but also sarcoid, have thick rim enhancement and might also be associated with cord oedema.
Pilocytic astrocytoma WHO grade I represents 5-10% of all gliomas and is the most common brain tumour in children (80% of them below 20 years of age), being a rare diagnosis in the adult population [4]. Most spinal astrocytomas are located in the upper thoracic spinal cord followed by cervical spine, very rarely in the conus medullaris. [4, 5]
A wide spectrum of clinical presentations exists. [5]
They are usually eccentric within the spinal cord. Usually they have inhomogeneous enhancement. Thus the classic MRI appearance of a spinal cord pilocytic astrocytoma is that of a cord-enlarging mass with associated oedema, located most often eccentrically, with a patchy and irregular pattern of contrast enhancement. [2]
The histological appearance is characterized by a biphasic pattern of two astrocyte populations: Compacted bipolar cells with Rosenthal fibres, and a loose-textured multipolar cell with microcysts and eosinophilic granular bodies. [2, 3]
As take home point we think low grade astrocytoma should be included in the differential diagnosis when ring or little enhancement in a predominantly cystic tumour of the cord is shown.
Spinal pilocytic astrocytoma, WHO grade I
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The patient is a 39-year-old female complaining of low back pain radiating to the right lower limb, accompanied by sensory abnormalities. MRI shows an occupying lesion in the spinal canal at the lumbar level, primarily within the spinal cord itself (evident from cord expansion). On T2-weighted images, the lesion demonstrates a long T2 hyperintensity, with significant intramedullary edema extending both cranially and caudally. Contrast-enhanced scans reveal ring or marginal enhancement, with relatively thin areas of enhancement.
The lesion is roughly located from the lower thoracic segment to the lumbar spinal cord (near or involving the conus medullaris), appearing as an elliptical or irregular cystic-solid mixed-signal mass. No obvious bony destruction or spinal canal stenosis is observed in the surrounding vertebral bodies or spinal canal.
These tumors may exhibit mixed cystic-solid changes, with ring-like or patchy enhancement, often accompanied by significant intramedullary edema and cord expansion. While the patient’s age is slightly older than typical, this remains a major consideration.
A common intramedullary tumor in adults. It can present as a cystic or solid lesion with varying degrees of enhancement. Although classically found in the lower cervical or thoracic spinal cord, it can occur in the conus medullaris. Intramedullary edema is also frequently observed.
These lesions can sometimes appear as mixed cystic-solid masses or display flow voids, especially in hemangioblastoma, which is often located in the posterior fossa or thoracic cord and may be associated with vascular proliferation. Lipomas typically show high signal intensity on T1-weighted images. Based on the imaging features in this case, these diagnoses are less typical but should be included in the differential considerations.
Thick-walled ring enhancement could suggest tuberculoma or granulomatous inflammation, but these lesions usually have systemic manifestations or corroborative laboratory findings (elevated ESR, positive tuberculous serology, etc.), and the patient’s history may involve infectious or immune-related factors.
An epidermoid cyst can show thin-walled enhancement, with the cyst fluid typically presenting as low signal on T1 and high signal on T2. However, significant intramedullary edema is less common. In the presence of pronounced edema, other tumor entities should be ruled out first.
Considering the patient’s lumbosacral pain, the intramedullary lesion with ring enhancement on MRI, as well as the intramedullary edema and mixed cystic-solid appearance, the most likely diagnosis is a low-grade spinal astrocytoma (e.g., pilocytic astrocytoma). Because this type of tumor is relatively uncommon in the adult spinal cord, pathological examination or surgical exploration is needed for confirmation. If in doubt, further imaging follow-up or biopsy can be performed.
Treatment Plan:
Rehabilitation Program:
Disclaimer: This report is solely based on current clinical and radiological data and is intended for reference only. It is not a substitute for in-person consultation or professional medical advice. Definitive treatment decisions should be made under the guidance of a specialist physician.
Spinal pilocytic astrocytoma, WHO grade I
