CASE 16251 Published on 05.12.2018

A case report on indirect visualisation of subacute superior gluteal nerve entrapment due an unidentified cause.


Musculoskeletal system

Case Type

Clinical Cases


Aneeq Ahmed, Jim Crotty

University Hospital Limerick ; Dooradoyle V94 F858 Limerick , Ireland;

47 years, female

Area of Interest Musculoskeletal system, Neuroradiology brain ; Imaging Technique MR
Clinical History
A 47-year-old female presented with a 3 month history of non-specific, progressively worsening, sharp buttock pain which was exacerbated by exercise and relieved by rest. On clinical examination there was weakness in abduction of the hip on the right side. No obvious cause was identified.
Imaging Findings
MRI was used to confirm the diagnosis of right superior gluteal nerve impingement in this case. Coronal and sagittal images from T1 weighted and STIR sequences are displayed highlighting subacute superior gluteal nerve impingement. Using MRI, it was not possible to directly visualise the nerve entrapment. However, the nerve impingement was indirectly visualised as hyper-intensity of right tensor fasciae latae, gluteus medius and gluteus minimus muscles on STIR sequences (Fig 1, Fig 2 and Fig 3). On T1 weighted images there was mild increase in signal intensity in right tensor fasciae latae, gluteus medius and gluteus minimus, indicating fatty changes (Fig 4, Fig 5 and Fig 6).
The superior gluteal nerve (SGN) is formed by the posterior roots of L4, L5, and S1 [1]. It exits the pelvis between the upper surface of the piriformis muscle and osseous border of the greater sciatic foramen; entering the deep gluteal space [1]. As the SGN supplies motor branches to the gluteus medius and minimus, nerve injury usually manifests as weakness in abduction of the hip and a Trendelenburg gait [1]. It doesn’t have any sensory branches [2].

Injury to the SGN is common during the direct lateral approach to the hip during arthroplasty [3, 4, 5], due to local buttock trauma, pelvic fracture, and after buttock injections [6, 7]. It may also occur due to compression by anterior-superior tendinous fibers of the piriformis muscle [8] or by prominent osteophytes, bony excrescences related to fractures, and infectious and inflammatory processes, as it exits the pelvis [9].

MRI is the imaging modality of choice with regards to the presence, extent of and site of nerve injury, and differentiating between surgically treatable and untreatable causes [1, 10]. The degree and duration of injury determines the extent of neural recovery [9].

The SGN can be seen on coronal and sagittal images as it exits the pelvis, along the bony brim, in the suprapiriformis foramen [1, 9], and on axial images as it travels laterally through the fat plane between the gluteus minimus and medius muscles [1]. On T1-weighted MR images, nerves have intermediate signal intensity, while being isointense or mildly hyperintense to muscle on T2-weighted and short inversion time inversion-recovery (STIR) [9] primarily due to normal endoneural fluid [11].

Motor neuropathy in gluteus medius and minimus can used to indirectly visualise SGN impingement [12]. In acute and subacute presentation, this will appear as high-intensity for denervated muscles on T2-weighted and STIR images, while appear as normal intensity on T1 weighted images [13]. The normal architecture and size of the muscle are still preserved, with no abnormalities of subjacent fascia. As the denervation progresses, intensity of the muscle on T1-weighted image will increase [9]. In chronically denervated muscles, atrophy and fatty replacement[14], manifests as non-specific increase in signal intensity on both T1 and fluid sensitive images, indicating irreversibility [9].

Teaching point:
SGN entrapment is a cause of hip pain which may be easily missed. Knowledge of nerve pathway and distributions are necessary to correctly visualise, directly or indirectly, SGN entrapment.

Written informed patient consent for publication has been obtained.
Differential Diagnosis List
Subacute superior gluteal nerve entrapment
Local buttock trauma
Compression by anterior-superior tendinous fibers of the piriformis muscle
Compression due to osteophytes
Damage due to infectious or inflammatory processes
Final Diagnosis
Subacute superior gluteal nerve entrapment
Case information
DOI: 10.1594/EURORAD/CASE.16251
ISSN: 1563-4086