Abstract
Malignant otitis externa is a severe, rare infective condition of the external auditory canal and skull base. The diagnosis is generally made from a range of clinical, laboratory, and imaging findings. Technetium 99m methylene diphosphonate bone scintigraphy is known to detect osteomyelitis earlier than computed tomography. The authors present a patient with bilateral malignant otitis externa where the extent of skull base involvement was determined on 3-phase bone scintigraphy with single photon emission computed tomography/computed tomography.
1
Introduction
Malignant otitis externa (MOE) is a severe, rare infection of the external auditory canal and skull base . The diagnosis is generally made from a range of clinical, laboratory, and imaging findings. Characteristic computed tomography (CT) findings of bone erosion and decreased skull base density may be discovered late in the course of the disease . Scintigraphy is a sensitive technique for early detection of bony infections. A combination of CT and tomographic scintigraphy may provide more specific information in identifying the extent of skull base osteomyelitis in such cases.
2
Case report
A 69-year-old diabetic man presented with vertigo, pain, and discharge from both ears and left facial palsy. Granulation tissue was found in the external auditory canal of both ears. Triphasic bone scintigraphy of the skull was performed under a dual-head γ camera (Infinia Hawkeye; GE, Milwaukee, WI) after intravenous injection of 740 MBq (20 mCi) of technetium Tc 99m methylene diphosphonate (MDP). Initial dynamic images were acquired at the rate of 2 seconds per frame, followed by a static image, comprising the soft tissue (blood pool) phase, 1 minute after injection. Delayed static images were then acquired after 3 hours, followed by single photon emission computed tomography/CT (SPECT/CT) of the skull. Increased perfusion was seen in both temporal regions in the initial dynamic images (not shown here), followed by increased uptake of the tracer in the blood pool ( Fig. 1 A ) and delayed images in the same region ( Fig. 1 B). Hybrid SPECT/CT imaging ( Fig. 1 C and D) localized the abnormal tracer concentration to both mastoid bones with extension into the left petrous temporal and right zygomatic bones (arrows) and locally destructive changes. Ear swab culture showed growth of Pseudomonas aeruginosa , sensitive to amikacin and ceftazidime. Histopathology of the granulation tissue revealed features of acute inflammation with no evidence of malignancy. Antibiotic treatment was continued, with good clinical response.
2
Case report
A 69-year-old diabetic man presented with vertigo, pain, and discharge from both ears and left facial palsy. Granulation tissue was found in the external auditory canal of both ears. Triphasic bone scintigraphy of the skull was performed under a dual-head γ camera (Infinia Hawkeye; GE, Milwaukee, WI) after intravenous injection of 740 MBq (20 mCi) of technetium Tc 99m methylene diphosphonate (MDP). Initial dynamic images were acquired at the rate of 2 seconds per frame, followed by a static image, comprising the soft tissue (blood pool) phase, 1 minute after injection. Delayed static images were then acquired after 3 hours, followed by single photon emission computed tomography/CT (SPECT/CT) of the skull. Increased perfusion was seen in both temporal regions in the initial dynamic images (not shown here), followed by increased uptake of the tracer in the blood pool ( Fig. 1 A ) and delayed images in the same region ( Fig. 1 B). Hybrid SPECT/CT imaging ( Fig. 1 C and D) localized the abnormal tracer concentration to both mastoid bones with extension into the left petrous temporal and right zygomatic bones (arrows) and locally destructive changes. Ear swab culture showed growth of Pseudomonas aeruginosa , sensitive to amikacin and ceftazidime. Histopathology of the granulation tissue revealed features of acute inflammation with no evidence of malignancy. Antibiotic treatment was continued, with good clinical response.
