Acrel's pseudo-ganglion revisited: cadaveric and histological insights into a ganglioform wrist structure

Acrel's "pseudo-ganglion" is a ganglioform structure on the floor of the fourth dorsal extensor compartment at the wrist. Histological evidence contradicts this description and suggests that the structure lacks neuronal cell bodies, supporting the term pseudoganglion. The aim of the current anatomical and histological study of the terminal branch of the posterior interosseous nerve (PIN) in cadavers was to determine the nature of this ganglioform swelling.

Thirty wrists from fifteen formalin-fixed cadavers were carefully dissected to locate the terminal PIN and any ganglioform structures present. Appropriate areas were sampled and stained with the conventional hematoxylin and eosin to assess the absence or presence of ganglionic and other cellular elements.

In all specimens, the ganglioform swelling with distally directed fine nerve branches was a constant finding, with the swelling located proximal to the extensor retinaculum in the majority of cases (56.7%). The ganglioform swellings showed fascicular derangement, extensive connective tissue agglomeration, and a complete absence of neuronal cell bodies, thus histologically confirming their non-ganglionic nature. Approximately half of the sub-retinacular cases showed evidence of chronic compressive neuropathy characterized by endoneurial and perineurial fibrosis.

The terminal swelling of the PIN represents a non-ganglionic pseudoganglion with fascicular disorganization and connective tissue proliferation. The fact that the swelling may occur under the extensor retinaculum and exhibit compressive changes suggests that chronic mechanical irritation may be involved in its pathogenesis. Awareness of this terminal swelling is important to avoid labeling it as a true ganglion and to appreciate the pathology of the distal posterior interosseous nerve.