Cystic lesions of peripheral nerves: Are we missing the diagnosis of the intraneural ganglion cyst?

Table 1 Inclusion criteria for intraneural ganglion cyst

Multilocular elongated hyperintense cystic mass on T2 weighted imaging

Distributed along the course of a peripheral nerve and its branches

Extension along the articular branch to the adjacent joint

Denervation changes of the muscles supplied by involved nerve

Table 2 Epidemiological data of patients diagnosed with cystic lesions related to the nerve

Patient data	Intraneural ganglion cyst	Extraneural ganglion cyst	Para-labral cyst	Cystic schwannoma	Nerve abscess
Total number of lesions	13	10	6	8	8
Mean age (yr) SD	38.2 14.66	30.5 16.42	32 3.94	42.6 10.79	28.2 12.84
Common symptoms	Pain along distribution of nerve, motor weakness	Pain and swelling	Pain and weakness of external rotators	Parasthesia, pain along distribution of nerve	Parasthesia and weakness
Male:female ratio	10:2	6:4	6:0	5:3	8:0
Nerves involved	CPN 7	Near	Near	CPN 3	Ulnar 51
	Tibial 2	CPN 9	SSN 6	Median 2	CPN 21
	Suprascapular 2	Radial 1		Sciatic 1	Median 3
	Prox. Sciatic 1			Tibial 1	Radial 31
	Obturator 1			Radial 1
Number who underwent surgery	6/13	10/10	6/6	8/8	3/8
Correct diagnosis on MRI	7/13	8/10	6/6	8/8	8/8

¹Combined involvement of multiple nerves. MRI: Magnetic resonance imaging; CPN: Common peroneal nerve.

Table 3 Summery of magnetic resonance imaging findings of intraneural ganglion cyst of peripheral nerves

SN	Involved nerve	Extension			Labral or capsular tear	Joint abnormality	Muscledenervation
		Anatomical extent along the parent nerve	Branches	Intra-articular extension
1	Right CPN	Upto sciatic bifurcation	Recurrent articular	Anterior aspect of PTF joint	Negative	-	Muscles of anterolateral compartment of leg
2	Left CPN	Upto posterolateral fibular head	Recurrent articular, deep peroneal	Anterior aspect of PTF joint	Negative	-	-
3	Right CPN	Upto sciatic bifurcation	Recurrent articular, superficial and deep peroneal	Anterior aspect of PTF joint	Negative	-	Muscles of anterolateral compartment of leg
4	Left CPN	Upto posterolateral fibular head	Recurrent articular, deep peroneal	Anterior aspect of PTF joint	Negative	-	-
5	Left CPN	Upto posterolateral fibular head	Recurrent articular, deep peroneal	Anterior aspect of PTF joint	Negative	-	Muscles of anterolateral compartment of leg
6	Right CPN	Upto posterolateral fibular head	Recurrent articular	Anterior aspect of PTF joint	Negative	-	Muscles of anterolateral compartment of leg
7	Right CPN	Upto neck of fibula	Recurrent articular	Anterior aspect of PTF	Negative		-
8	Right obturator	Along the lateral pelvic wall to pelvic brim	Anterior division	Anteromedial aspect of hip joint	Negative	-	Adductor brevis and magnus
9	Right suprascapular	Suprascapular to spinoglenoid notch	-	-	Negative	-	Supra and infraspinatus
10	Left proximal sciatic	At sciatic notch	Articular	Posteromedial aspect of hip joint	Negative	-	-
11	Right tibial	Upto tibial nerve	Articular, branch to popliteus muscle	Posterior aspect of PTF joint	Negative	-	-
12	Left tibial	Upto sciatic bifurcation	Articular, branch to popliteus muscle, branch to tibialis posterior muscle	Posterior aspect of PTF and knee joints	Negative	-	Popliteus and tibialis posterior
13	Right suprascapular	From the level of AC joint to below the spinoglenoid notch	Articular branch to AC joint	AC joint	Negative	-	-

PTF: Proximal tibiofibular; AC: Acromioclavicular; CPN: Common peroneal nerve.

Table 4 Magnetic resonance features differentiating intraneural ganglion cyst from extraneural ganglion cyst

	Intraneural ganglion cyst	Extraneural ganglion cyst
Cyst size	Small	Large
Cyst shape	Tubular beaded configuration	Globular
Cyst pattern and location	It is along the course of the nerve and its branches with no fat plane between the cyst and the nerve	It does not follow the course of the nerve; the nerve is seen separately from the cyst with an intervening preserved fat plane; usually located in between the fibula and peroneus longus muscle, with or without an intramuscular extension
PTF joint connection	Is present and the tail lies anteromedial to proximal fibula between 10-12 o’clock position on axial MR images	Is present but located more superiorly and anterolateral to the proximal fibula at 12-2 o’clock position on axial MR images
Relation with fibula	The extension of the cyst along the articular branch appears to cross the fibula from medial to lateral (“Transverse limb sign”)	The cyst never crosses the fibula and always lies anterior, anterolateral or lateral to the fibula (Absent “Transverse limb sign”)
Muscle denervation	Common	Uncommon

MR: Magnetic resonance; PTF: Proximal tibiofibular.