Background The classical clinical picture of inferior oblique pseudopa
lsy can be caused by (1) a tight connection between the superior obliq
ue insertion and the trochlea and (2) a thickening of the tendon restr
icting the passage of the tendon through the trochlea. The entity may
be congenital or acquired and constant or intermittend. A spontaneous
cure is possible. Question and results We looked for the cause of the
inferior oblique pseudopalsy in 41 patients operated on during the las
t 15 years. 31 patients had a congenital and 10 an acquired inferior o
blique pseudopalsy. None of these cases had an alteration of the sheat
h of the superior oblique tendon. Instead, we found a tight band at th
e posterior border of the tendon between the trochlea and the sclera i
n all patients with a congenital inferior oblique pseudopalsy. Resecti
on of this band, either in tote or solely of the portion near the scle
ra resulted in a normalisation of the active and passive elevation in
adduction. In some patients a second operation was necessary. The 'V-p
attern' existing preoperatively regressed in part or completely during
the 1.5 postoperatives years. A consecutive superior oblique palsy wa
s seen in one case only. Conclusion A tight band at the posterior bord
er of the ten don between the trochlea and the sclera explains the con
genital variety of the inferior oblique pseudopalsy in many cases. A t
hickening of the tendon restricting the passage of the tendon through
the trochlea may play a role in some cases, particularly in those with
a spontaneous cure, but the surgical approach used in this series of
patients was not suited to verify this mechanism. Name of the syndrome
The pathognomonic signs of the inferior oblique pseudopalsy, restrict
ion of active and passive elevation in adduction, were first described
by Jaensch in 1928 in an acquired case, and Jaensch already suggested
a tight band between the trochlea and the sclera as the mechanism. Br
own, in 1950, only added the congenital variety. Since we owe the firs
t description of the inferior oblique pseudopalsy to Jaensch, his name
should be included in the designation of the syndrome, i.e., it shoul
d be called ''Jaensch-Brown syndrome'' rather than ''Brown's syndrome'
'. The name suggested by Brown, ''superior oblique tendon sheath syndr
ome'', is no longer appropriate since the tissue surrounding the super
ior oblique tendon is normal.