Pearls & Oy-sters: Good recovery following cerebral fat embolization with paroxysmal hyperactivity syndrome

PEARLS

• Cerebral fat embolism syndrome (FES) most often presents with gradual decline in level of consciousness and worsening motor responses.

• MRI shows innumerable punctate foci of restricted diffusion in a “starfield” pattern, which subsequently coalesce into confluent lesions.

• Paroxysmal sympathetic hyperactivity (PSH) after FES may not be a poor prognostic sign and good recovery can occur.

OY-STERS

• FES is a triad of CNS dysfunction (rapidly developing coma), petechial hemorrhage (typically on upper body), and acute pulmonary injury (hypoxemia, tachypnea).

• PSH syndrome is characterized by episodic fever, diaphoresis, hypertension, tachycardia, tachypnea, and rigidity. PSH has traditionally been observed in traumatic brain injury patients and is generally associated with a poor outcome.

CASE 1

A 21-year-old previously healthy man had a right closed midshaft femur and patella fracture from a motor vehicle accident (figure, A). Four hours later, he underwent right knee irrigation and debridement followed by a proximal tibial traction pin placement. Ten hours after this procedure, he became confused, agitated, hypoxemic (oxygen saturation 60%), hypotensive (blood pressure 86/58 mm Hg), and tachycardic (pulse 140/min). He was now comatose with spontaneous extensor responses. Skin petechiae were noted. Chest CT showed bilateral pulmonary edema. Transthoracic echocardiogram (TTE) showed dyssynchronous interventricular septum and elevated right ventricular systolic pressure consistent with acute pulmonary hypertension. For several days, he remained comatose and developed episodes of fever, tachycardia, and profuse sweating. He was diagnosed with PSH and received propranolol, gabapentin, and clonidine. To better control these episodes, lorazepam, fentanyl, and morphine were also administered. Brain MRI on day 5 showed multiple diffuse hypointense foci on susceptibility-weighted sequence (SWI) and innumerable foci of reduced diffusion in a “starfield” pattern, compatible with fat embolism (figure, B and C).

• Download figure
• Open in new tab
• Download powerpoint

Figure Brain MRI shows changes over time in 2 patients with cerebral fat embolism

Upper row (case 1): Radiograph of the right leg shows closed midshaft femur fracture (A); day 5, axial susceptibility-weighted imaging sequence shows multiple punctate foci of hypointense signal throughout the brain (marked by black arrow) (B); multiple foci of restricted diffusion (starfield pattern) in diffusion-weighted imaging sequence (DWI) (C) and follow-up MRI on day 23 show resolution of some lesions in DWI sequence (D). Lower row (case 2): Radiograph of the left foot and calcaneus shows innumerable tiny metallic shot fragments in the soft tissues and bones and multiple fractures of the calcaneus associated with soft tissue swelling (E); first MRI done on day 1 shows multiple areas of restricted diffusion in DWI sequence in characteristic starfield pattern (F); follow-up MRI on day 7 shows progression of tiny lesions to confluent pattern (G); follow-up MRI on day 30 shows marked resolution of the cytotoxic edema (H).

He started to open his eyes at 2 weeks and eventually made a remarkable recovery. On a follow-up MRI there was evolution of the punctate restricted diffusion to confluent signal change in the caudate and splenium of the corpus callosum (figure, D). Neuropsychometric testing showed impairments in cognitive speed and executive function. At 12 months follow-up, he was able to work part time.

CASE 2

A 42-year-old man was shot in the left foot by his 12-year-old son during a hunting trip. X-ray showed multiple fractures of the left calcaneus associated with soft tissue swelling (figure, E). Four hours later, his blood pressure transiently declined to 83/55 mm Hg. His arterial blood gas showed pH 7.39, Po₂ 158 mm Hg, Pco₂ 37 mm Hg, and FIO₂ 40% with an increased arteriolar-alveolar gradient of 81. He was groaning, opening his eyes spontaneously, and not tracking. There was increased muscle tone, hyperreflexia, and bilateral Babinski signs. He gradually became less responsive and 5 hours later developed extensor posturing. He was intubated for airway protection. Chest x-ray was normal. Brain MRI performed 30 hours later showed scattered foci of reduced diffusion in a starfield pattern (figure, F). TTE showed intrapulmonary shunting. He became tachycardic (pulse up to 148 beats/min) and febrile (39°C), and manifested profuse sweating. He was treated with gabapentin, hydromorphone, and metoprolol. He had spontaneous eye opening the next day. Follow-up MRI after the first week demonstrated near resolution of prior diffusion-weighted imaging (DWI) lesions (figure, G) with continuous improvement at 4 weeks (figure, H). He was transferred to a nursing home. The patient improved slowly and after 6 months he was living at home with family. His residual deficits included problems with speech, memory (short and long term), irritability, left upper extremity spasticity, left ulnar compression neuropathy, peripheral neuropathy, and antalgic gait.