A 16-year-old boy presented to the emergency department with severe epigastric pain, headache and ascending lower limb weakness 1 hour after eating raw salmon. The weakness ascended rapidly over the next hour to involve the upper limbs. In hospital, he was alert, but was soft-voiced and in obvious respiratory distress. He had tachycardia (heart rate, 110 beats per min), hypertension (blood pressure, 205/128 mmHg), tachypnoea (22 breaths per min) and oxygen saturation of 89% (using a non-rebreathing oxygen mask). Although his sensation and mental state appeared normal, he had profound quadriparesis. Pupils were 3 mm in diameter, equal and sluggishly reactive to light. Because of a rapid deterioration in his respiratory status, the patient was intubated, ventilated, and sedated with a propofol infusion before a more complete neurological examination could be completed.

The patient’s medical history included thalassaemia minor and a short viral illness 2 weeks previously. He denied using any regular medications or substance misuse.

Initial chest radiography revealed clear lung fields, but, 10 minutes after intubation, pinkish frothy sputum was noted from the endotracheal tube, and there were widespread crackles. An urgent echocardiogram showed severe global hypokinesis with a left ventricular ejection fraction estimated as less than 30%. Laboratory tests revealed neutrophilia, but all other results of a full blood count, serum electrolyte concentrations, renal function, liver function tests and coagulation screen were normal. Serum creatine kinase and creatine kinase-MB concentrations were raised, and peaked the following day at 2716 U/L (reference range [RR], 30–135 U/L) and 10 μg/L (RR, < 0.7 μg/L), respectively, suggesting myocardial injury. An electrocardiogram showed sinus rhythm with voltage criteria for left ventricular hypertrophy, but no acute ischaemic changes.

Provisional diagnosis at this stage was a neurological or toxicological aetiology. The fact that the patient’s mother also ate the salmon without becoming unwell counted against seafood poisoning but did not exclude it (eg, in puffer-fish poisoning, a specific part of the fish is most poisonous).

To exclude a cervical lesion, magnetic resonance imaging (MRI) of the spine and brain was performed urgently, with the intention of proceeding to nerve conduction studies if MRI results were normal. The MRI showed an extensive intramedullary haemorrhage within the spinal cord, originating at the T7/T8 vertebral level, and extending from the conus caudally to the cervicomedullary junction rostrally (Box 1).

The patient was managed supportively in the intensive care unit, with complete resolution of pulmonary oedema and normalisation of cardiac function by Day 3. A spinal angiogram confirmed the presence of an arteriovenous malformation arising from the anterior spinal cord at the T9 vertebral level. The malformation was excised the following week, and histopathological examination of the resection specimen confirmed the radiological diagnosis (Box 2).

After 6 months of intensive rehabilitation, the patient had restored power in one arm, but remained paralysed below the T9 cord level.

Initially, this case represented a diagnostic challenge, with acute onset, rapidly progressive ascending paralysis associated with left ventricular failure, and a history of seafood ingestion. MRI gave the correct diagnosis, obviating the need for peripheral neurophysiological investigations. Useful clues to the diagnosis of myelopathy, such as sphincter dysfunction and the level of sensory loss, were difficult to assess because of the patient’s sudden cardiorespiratory deterioration. The initial differential diagnosis is summarised in Box 3.

1 Magnetic resonance image of the cervical spinal cord

A sagittal T2-weighted image showed a high signal (arrow) within the cervical cord caused by blood breakdown products (intracellular methaemoglobin).

2 Lesion excised from the spinal cord

Histopathological examination of the resection specimen showed abnormally clustered vessels of venous (V) and arterial (A) type intermingled with spinal nerve bundles (N). This vascular configuration is typical of an arteriovenous malformation. (Haematoxylin and eosin stain; original magnification, × 40.)