Neurosarcoidosis as a Cause of Longitudinally Extensive Myelitis: Neuroimaging Clues for Diagnosis.

INTRODUCTION

The clinical presentation of neurosarcoidosis is highly variable, and in rare instances, isolated spinal cord involvement may be the sole clinical manifestation. Extensive spinal cord involvement revealed on magnetic resonance imaging (MRI) of the spine is a key finding in spinal neurosarcoidosis. The presence of longitudinally extensive transverse myelitis, defined as lesions extending more than three vertebral segments on MRI spine, implies a wide differential diagnosis and neurosarcoidosis as a cause may be easily overlooked with grave consequences.

CASE REPORT

A 48-year-old female presented to us with a history of symmetric, tingling paresthesia in the lower limbs for the past 9 months, which progressively ascended to involve the trunk and neck. On examination, she had loss of joint position and vibration sensations over the lower limbs and trunk, a sensory level at the mid-thoracic region, spasticity of bilateral lower limbs, and a positive Romberg's sign. MRI spine and brain showed longitudinally extensive T2 and fluid-attenuated inversion recovery hyperintensities, involving the posterior column with contrast enhancement [Figure 1]. MRI brain was normal. Causes of longitudinally extensive tract specific spinal cord lesions including neuromyelitis optica spectrum disorders (NMOSDs), paraneoplastic myelopathies, and Vitamin B12 deficiency were initially considered. Laboratory tests revealed normal levels of serum Vitamin B12 levels (1085 pg/ml; normal range 211–911 pg/ml) and serum copper (115 μg/dl; normal range 85–155 μg/dl) whereas serum aquaporin 4 antibody was negative. Screening for blood biomarkers for cancer including cancer antigen (CA)-125, Carcino Embryonic Antigen, CA 19-9, and alpha-feto protein were negative. Cerebrospinal fluid examination revealed five cells (all lymphocytes), mildly elevated proteins (57 mg/dl; normal 15–45 mg/dl), and normal sugar (66 mg/dl; normal 45–80 mg/dl). Computerized tomography (CT) of the thorax showed paratracheal, hilar, and subcarinal nodes in addition to the right upper lobe fibrosis. Serum angiotensin-converting enzyme levels were normal (50 U/L; normal range 8–53 U/L). CT-guided transthoracic biopsy of the mediastinal lymph nodes was then performed and histopathologic evaluation revealed noncaseating granulomas. Staining and polymerase chain reaction for mycobacterium tuberculosis was negative. A diagnosis of systemic sarcoidosis with neurological involvement was made, and the patient was started on intravenous followed by oral steroids. She noted significant improvement in clinical symptoms with treatment.

Figure 1

Magnetic resonance imaging spine T1 postcontrast showing multifocal areas of T2 hyperintensity with associated contrast enhancement (arrows), involving the posterior aspect of the spinal cord

DISCUSSION

Spinal cord involvement in sarcoidosis is a rare complication which affects about 0.43%–1% of patients and may even be the initial and solitary clinical presentation.[1] Characteristic MRI findings in spinal neurosarcoidosis include longitudinally extensive spinal lesions with dorsal subpial contrast enhancement.[2] A “trident” pattern has also been recently reported, but was not present in our patient.[3] Longitudinally extensive spinal lesions may also be seen in NMOSD, paraneoplastic myelopathies, Vitamin B12 or copper deficiencies, and HIV myelopathy.[4] However, the presence of dorsal subpial enhancement extending >2 vertebral segments is a distinct feature of neurosarcoidosis and is an important clue to differentiate it from other causes mentioned above. Flanagan et al. reported the presence of dorsal subpial enhancement as a reliable sign in differentiating neurosarcoidosis from NMOSD.[2] The presence of this sign would therefore imply a prioritization of chest computed tomography (CT) or positron emission tomography CT to look for hilar lymph nodes. Extensive tract or gray matter-specific MRI changes are strongly associated with paraneoplastic myelopathies, particularly lung malignancies which may also show hilar lymphadenopathy.[5] Neurosarcoidosis and paraneoplastic myelopathies may mimic each other closely, and a histological diagnosis becomes mandatory for crucial therapeutic and prognostic decision-making. Nevertheless, the presence of dorsal subpial enhancement as shown in Figures 1 and 2 is a valuable clue which would favor a diagnosis of spinal neurosarcoidosis.

Figure 2

Magnetic resonance imaging spine axial T1 postcontrast showing dorsal subpial contrast enhancement

CONCLUSIONS

The presence of dorsal subpial enhancement on MRI spine is an important radiologic sign for diagnosing spinal neurosarcoidosis.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.