Cervical intradural disc herniation (CIDH) is an uncommon spinal disorder characterized by penetration of nucleus pulposus through the dura mater into the subarachnoid space, causing direct compression of the spinal cord or nerve roots. CIDH accounts for less than 0.3% of all disc herniations, with cervical cases comprising only about 3% of intradural occurrences (1). Since its initial description by Marega in 1959, fewer than 50 confirmed cases have been reported worldwide as of 2025 (2–4). Owing to its rarity, nonspecific imaging features, and limited clinical awareness, preoperative diagnosis remains challenging, with an estimated detection rate of only 13% (2).

We report a spontaneous case of CIDH in a middle-aged man presenting with acute Brown-Séquard syndrome. T2-weighted MRI showed marked hyperintensity at the C4/5 disc, and intraoperatively, the disc material demonstrated increased water content compared to typical degenerative discs.These features may represent a previously underrecognized diagnostic clue. In cases of acute and severe cervical myelopathy with similar radiologic and intraoperative findings, surgeons should maintain a high index of suspicion for CIDH and prepare for potential dural tears and cerebrospinal fluid leakage during preoperative and intraoperative planning.

A 55-year-old man presented with sudden-onset limb weakness lasting one day, without any identifiable precipitating event. He had been ambulatory the day prior. After excluding intracranial pathology, he was referred to the orthopedic department. On admission, he demonstrated significant weakness in the left extremities and was unable to ambulate independently. Neurological examination revealed asymmetric motor deficits with ASIA motor scores (right/left): Biceps 4/3, Wrist extensors 4/3, Triceps 4/3, Finger flexors 3/2, Finger abductors 3/2, Iliopsoas 4/0, Quadriceps 4/2, Tibialis anterior 4/2, Extensor hallucis longus 4/2, Gastrocnemius 4/2. Sensory testing showed complete loss of pain and temperature sensation on the right side. Deep tendon reflexes—including triceps, patellar, and Achilles—were absent bilaterally. No clonus or Hoffman's sign was present, and sphincter function remained intact. The presentation was consistent with Brown-Séquard syndrome. Sagittal T2-weighted MRI revealed marked hyperintensity at the C4/5 disc compared to adjacent levels, with a space-occupying lesion posterior to the C5 vertebral body causing significant spinal cord compression (Figure 1). The thoracic and lumbar spine appeared normal. Cervical CT showed no evidence of ossification of the posterior longitudinal ligament (OPLL), and no obvious abnormalities were observed in the vertebral body bone. Preoperative and postoperative hematological and inflammatory markers showed no evidence of infection.

A preliminary diagnosis of cervical disc herniation was made. Due to rapid neurological decline, emergency anterior decompression was performed. Partial resection of the anterior longitudinal ligament and C4/5 disc exposed disc tissue with notably increased water content, contrasting with the typically dry, fibrotic appearance of degenerative discs. Upon reaching the level of the posterior longitudinal ligament, a small amount of clear fluid was observed, but no obvious compressive material was identified, raising suspicion for CIDH. Due to limited visualization, subtotal C5 corpectomy was performed. Intraoperative exploration revealed a longitudinal ventral dural tear, approximately 2 cm in length, through which disc fragments had herniated into the subarachnoid space. The dural margins were defined, the tear gently expanded, and the intradural fragments were removed under microscopic guidance (Figure 2). Histopathological examination confirmed the tissue to be nucleus pulposus, with an oval-like shape and a maximum diameter of approximately 1 cm. Primary dural repair was achieved with sutures (Figure 2), augmented with fibrin glue and autologous subcutaneous cervical fat. The procedure was completed with anterior cervical corpectomy and fusion (ACCF). Postoperative rehabilitation led to substantial recovery. At three months post-operation, following rehabilitation therapy, the patient was able to walk with a cane, indicating initial functional recovery (Figure 3). At one-year follow-up, motor strength had returned to grade 5 except for mild residual weakness in the intrinsic muscles of the left hand.

This case, combined with a literature review, focuses the discussion on three key aspects: clinical and radiological features, the pathophysiological basis of T2 hyperintensity and intraoperative findings, and surgical considerations.

Cervical intradural disc herniation remains a rare and diagnostically challenging entity due to its nonspecific clinical and radiological features. This case underscores the diagnostic relevance of disc-level T2 hyperintensity and intraoperative identification of disc tissue with increased water content as potential surrogate markers of dural penetration. Early recognition of these features may enhance preoperative suspicion and guide surgical planning. Intraoperative dural repair and thorough decompression are critical for achieving favorable outcomes, while anterior fusion is essential for maintaining spinal stability following extensive ventral exposure. Increased awareness of these diagnostic and surgical considerations may facilitate earlier detection and optimize the management of this rare but clinically significant condition.