Entrapment neuropathies of the fibular nerve and its branches are often underdiagnosed
due to the lack of reliable diagnosis using clinical examination and electrophysiologic
evaluation. Most fibular nerve compressions may be classified into 2 broad categories:
(a) mechanical causes, which occur at fibrous or fibro-osseous tunnels, and (b) dynamic
causes related to nerve injury during specific limb positioning. Foot drop resulting from
weakness of the dorsiflexor muscles of the foot is a relatively uncommon presentation
and closely related to L5 neuropathy caused by a disc herniation. However, we herein
describe a rare case of usually painless foot drop triggered by a cyst at the proximal
tibiofibular joint compressing the deep fibular nerve. The presence of multilevel disc
diseases made the diagnosis more difficult. Foot drop is highly troubling, and health
care providers need to broaden their search for the imperative and overlapping causes
especially in patients with painless drop foot, and the treatment is variable and should
be directed at the specific cause. The magnetic resonance imaging (MRI), including
high-resolution and 3D MR neurography, allows detailed assessment of the course and
anatomy of peripheral nerves, as well as accurate delineation of surrounding soft-tissue
and osseous structures that may contribute to nerve entrapment. Knowledge of normal
MRI anatomy of the nerves in the knee and leg is essential for the precise assessment of
the presence of peripheral entrapment conditions that may produce painless or painful
drop foot. In conclusion, we stress the importance of preoperative anatomic mapping of
entrapment neuropathies to minimize neurological complications.
Key words: Foot drop, fibular nerve, ganglion cyst, proximal tibiofibular joint
Spontaneous Proximal Tibiofibular Joint Ganglion Cyst as a Rare Cause of Acute Foot Drop: A Case Report