Spinal cord compression and transverse myelitis — branching viva

Opening branch — the nine-year-old with nocturnal back pain and a weak leg

A previously well nine-year-old presents with three days of thoracic back pain that wakes him at night and is worse lying flat, then a weak left leg and acute urinary retention, with a T10 sensory level. The candidate must first state that the single most important next investigation is an emergency whole-spine MRI with gadolinium, performed within hours and never delayed for bloods or a lumbar puncture. The teaching point is that the MRI - not the history and not the bloods - resolves the fork between a compressive structural lesion, a surgical emergency needing dexamethasone and decompression, and an inflammatory transverse myelitis, a medical emergency needing methylprednisolone. [1] [4]

The examiner probes the symptom sequence and the urgency. The candidate describes the classic order of a compressive lesion - back pain, then radicular pain, then motor weakness, then a sensory level, then sphincter loss - and notes that nocturnal back pain worse lying flat, with a sensory level and urinary retention, is an established lesion with a narrow salvage window. The candidate states that ambulation at presentation is the single strongest predictor of outcome, and that the surgical decompression is timed within twenty-four to forty-eight hours of the loss of ambulation because the cord converts from a reversible oedematous phase to irreversible infarction within that window. [4]

Second branch — the febrile immunocompromised host with an epidural collection

The examiner switches to a febrile teenager with an indwelling central catheter, back pain, and a progressive paraparesis, whose MRI shows an epidural collection with adjacent discitis and vertebral body signal change and rim enhancement. The candidate identifies this as a spinal epidural abscess, names Staphylococcus aureus (including methicillin-resistant strains) as the predominant organism, and states the risk-factor cluster - immunocompromise, diabetes, an indwelling vascular catheter, a recent spinal procedure, skin or soft-tissue infection, and intravenous drug use. [5]

The examiner tests the management. The candidate states that the treatment is surgical drainage of the abscess plus targeted intravenous antibiotics for four to six weeks, with the decompression timed on the same twenty-four-to-forty-eight-hour principle as the malignant lesion. The teaching point is that the classic triad of back pain, fever, and a neurological deficit is present in only a minority, so each component is sought actively and the absence of one must not reassure. [1] [5]

Third branch — the twelve-year-old with a six-segment intrinsic lesion

The examiner switches to a twelve-year-old of East Asian ancestry with a three-day flaccid paraplegia, a T6 sensory level, and a viral prodrome two weeks earlier, whose MRI shows an intramedullary enhancing lesion spanning six vertebral segments. The candidate identifies this as a longitudinally extensive transverse myelitis, states that a lesion spanning three or more segments raises neuromyelitis optica spectrum disorder and myelin-oligodendrocyte-glycoprotein antibody-associated disease over multiple sclerosis (which is typically short, peripheral, and focal), and names the two antibody tests - serum aquaporin-4 IgG and serum MOG-IgG by a live cell-based assay - that resolve it. [2] [3]

The examiner probes the safety point and the treatment. The candidate states that a multiple-sclerosis disease-modifying therapy must never be started before the antibody status is known, because several of those drugs worsen AQP4-IgG-positive neuromyelitis optica spectrum disorder. The acute treatment is high-dose intravenous methylprednisolone at 20 to 30 mg per kg per day to a maximum of 1 g per day for three to five days, and because this may be a severe aquaporin-4-positive attack, early plasma exchange is favoured over intravenous immunoglobulin if the event is steroid-refractory at forty-eight to seventy-two hours. The candidate also reproduces the Transverse Myelitis Consortium 2002 progression-to-nadir window of four hours to twenty-one days. [1] [3]

Closing branch — the four-year-old who refuses to walk

The examiner closes with a four-year-old who simply refuses to walk and is irritable, with a distended bladder on examination. The candidate explains that a young child with a cord lesion often presents atypically - a refusal to walk, irritability, torticollis, abdominal pain, or acute urinary retention - rather than a verbal complaint the clinician can localise to the spine, and that this is exactly where the diagnosis is hardest and the threshold to scan must be lowest. A child who refuses to walk or who retains urine without an obvious explanation is imaged, not observed, and the emergency MRI is not deferred while a fever or a raised inflammatory marker is awaited. [2] [1]