Answer:
Left Common Peroneal Nerve entrapment Neuropathy at fibular head
Findings:
The left anterior and lateral compartment muscles ( extensor digitorum longus, Tibialis Anterior and Peroneus Longus) appear homogenously and diffusely hyperintense in T2W1 , STIR and Pd Fs sequences . There is no muscle enlargement . The adjacent fascia and subcutaneous tissue appear normal.
Discussion:
The findings in the given images are typical features of Acute muscle dennervation. The muscle involvement corresponds to common peroneal nerve distribution . Other causes of increased muscle signal intensity like muscle strain/tear can be excluded since they have inhomogenous appearance , while with infections , changes would be expected in the adjoining soft tissues. Patient clinically presented with Left foot Drop. Foot Drop is essentially a clinical and Electromyographic diagnosis. MRI easily reveals the Muscle dennervation as homogenous T2/STIR hyperintensity in Common peroneal nerve distribution .It also is useful to detect extrinsic causes of nerve compression like ganglion,synovial cyst or varicosities. Whenever increased signal intensity is noted in posterior tibial and popliteus muscles in addition to above three muscles , foot drop due to L5 radiculopathy has to be suspected and screening of lumbosacral spine has to be done.
References: MR Imaging in the Differential Diagnosis of Neurogenic Foot Drop AJNR Am J Neuroradiol 24:1283–1289, August 2003 MR Imaging of Entrap¬ment Neuropathies of the Lower ExtremityPart 2. RadioGraphics 2010; 30:1001–1019
Contributed By: Dr. Babu Peter MD, DNB
Associate Professor, B.I.R; Senior Consultant, Aarthi Scans, Chennai
Left Common Peroneal Nerve entrapment Neuropathy at fibular head
Findings:
The left anterior and lateral compartment muscles ( extensor digitorum longus, Tibialis Anterior and Peroneus Longus) appear homogenously and diffusely hyperintense in T2W1 , STIR and Pd Fs sequences . There is no muscle enlargement . The adjacent fascia and subcutaneous tissue appear normal.
Discussion:
The findings in the given images are typical features of Acute muscle dennervation. The muscle involvement corresponds to common peroneal nerve distribution . Other causes of increased muscle signal intensity like muscle strain/tear can be excluded since they have inhomogenous appearance , while with infections , changes would be expected in the adjoining soft tissues. Patient clinically presented with Left foot Drop. Foot Drop is essentially a clinical and Electromyographic diagnosis. MRI easily reveals the Muscle dennervation as homogenous T2/STIR hyperintensity in Common peroneal nerve distribution .It also is useful to detect extrinsic causes of nerve compression like ganglion,synovial cyst or varicosities. Whenever increased signal intensity is noted in posterior tibial and popliteus muscles in addition to above three muscles , foot drop due to L5 radiculopathy has to be suspected and screening of lumbosacral spine has to be done.
References: MR Imaging in the Differential Diagnosis of Neurogenic Foot Drop AJNR Am J Neuroradiol 24:1283–1289, August 2003 MR Imaging of Entrap¬ment Neuropathies of the Lower ExtremityPart 2. RadioGraphics 2010; 30:1001–1019
Contributed By: Dr. Babu Peter MD, DNB
Associate Professor, B.I.R; Senior Consultant, Aarthi Scans, Chennai