Syringobulbia

Syringobulbia is a fluid filled cavity (syrinx) within the brainstem, usually the medulla, often an upward extension of a cervical syrinx. It is associated with Chiari malformation type I, basilar invagination, posterior fossa tumour, trauma, arachnoiditis and, rarely, idiopathic or tumour related causes.

Pathophysiology. Disturbed cerebrospinal fluid flow at the craniocervical junction forces fluid into the central canal or parenchyma, with dissection along tracts and compression of nuclei and fibre tracts.

Dysphagia, dysarthria, tongue weakness and wasting with fasciculation, palatal weakness, facial numbness (onion skin pattern from trigeminal nucleus involvement), nystagmus (downbeat or horizontal), vertigo, hoarseness, sleep disordered breathing and sometimes limb signs of syringomyelia (cape like dissociated sensory loss, hand wasting). Course may be slow, with episodic worsening.

Red flags.

• Aspiration, respiratory compromise or sleep apnoea.
• Rapidly progressive bulbar signs.
• Cranial neuropathies or cardiovascular instability.

MRI of the brain, brainstem and whole spine shows a longitudinal cavity (CSF signal) in the medulla, with Chiari malformation, tumour or arachnoid scarring. Cine MRI assesses CSF flow at the foramen magnum. CT of the craniocervical junction for bone anomalies. Swallowing assessment (videofluoroscopy) and sleep study. Exclude tumour with contrast MRI.

Differential diagnosis.

• Brainstem glioma or haemangioblastoma with cystic component.
• Brainstem demyelination, Wallenberg syndrome and motor neuron disease (bulbar).
• Hydromyelia and myasthenia gravis.

Treat the cause. For Chiari malformation, posterior fossa decompression with or without duraplasty restores CSF flow and reduces the syrinx in most. Craniocervical stabilisation for basilar invagination or instability. Resect tumour or lyse adhesions if present. Shunting (syringo subarachnoid or syringo pleural) is reserved for persistent or enlarging cavities.

Bulbar and respiratory. Speech and language therapy, modified diet, gastrostomy for unsafe swallowing, non-invasive ventilation or CPAP for sleep disordered breathing.

Symptoms. Neuropathic pain with gabapentin 300 mg three times daily, increased as tolerated (adjust to eGFR), or amitriptyline, and physiotherapy.

Avoid neck manipulation, and hyperextension of the neck.

Monitoring. Neurological examination every 6 to 12 months, with MRI at 3 to 6 months after surgery and then as needed.

Referral and escalation. Refer to neurosurgery. Refer urgently for progressive bulbar signs or respiratory compromise.