Minimally invasive and surgical spine procedures are commonplace with various risks and complications.  Cranial nerve palsies, however, are infrequently encountered, particularly after procedures such as lumbar punctures, epidural anesthesia, or intrathecal injections and are understandably worrisome for clinicians and patients as they may be interpreted as secondary to a sinister etiology.  However, a less commonly considered source is pneumocephalus which may, in rare cases abut cranial nerves and cause a palsy as a benign and often self-resolving complication.

A middle-aged patient with a new diagnosis of high-grade mature T-cell non-Hodgkin lymphoma was admitted to the hospital for chemotherapy initiation.  The patient received the first cycle of CHOP chemotherapy and a first infusion intrathecal methotrexate infusion and post-procedurally, she developed a new onset of painless right-sided horizontal diplopia. The intrathecal injection was performed in prone positioning using a fluoroscopic guided 20-gauge spinal needle into the L2-L3 space.  Next, approximately 10ml of CSF fluid was collected followed by 12mg of methotrexate injection. CSF studies returned unremarkable.

Upon physical examination, there was a notable partial right-sided abducens palsy without any other focal neurological deficits. Non-contrast CT scan of the head demonstrated a pneumocephalus anterior to the pons and at the level of the clivus abutting the right abducens nerve (Figure 1). Follow-up brain MRI with contrast was unremarkable for other potential causes of this acute palsy presentation, including infections, stroke, or herniation from intracranial hypotension. The patient was monitored and managed expectantly without any acute interventions and upon follow-up in 24 hours there was complete resolution of her symptoms.