The main etiology described for DSN entrapment is hypertrophy of the middle scalene muscle causing compression of the nerve as it passes through.21 Mondelli et al.
Engel and Gatterman (7) suggest that the "cervical doorbell point is the location of the emergence of the anterior nerve root and is often mistaken for a "scalene trigger point".
(52) Plezbert and Nicholson (47) describe the successful treatment of a case of DSN neuropathy secondary to scalene myofascitis.
Functional anatomy of human scalene musculature: rotation of the cervical spine.
Figure 17 is a snapshot showing the needle passing between the middle and posterior scalenes or, in some cases, only through the middle scalene.
If the cause of the neuropathic pain is at the trunk or division level of the brachial plexus or if there is an excessive upward movement of the shaft of the first rib due to excessive pulling of the anterior and middle scalene, supraclavicular brachial plexus hydrodissection may provide better relief.
AS: anterior scalene, CA: carotid artery, IJV: internal jugular vein, LCa: Longus Capitis, LCo: longus colli, MS: middle scalene, PVF: prevertebral fascia, SCM: sternocleidomastoid, VN: vagus nerve, and VA: vertebral artery.
The image shows needle penetration through the middle scalene, with hydrodissection and fluid injection in the interscalene brachial plexus.
By seeding ice in a supercooled cloud by adiabatic expansion, Yamashita (1973) showed that in crystals grown at around -15[degrees]C no trigonal or scalene hexagons formed out of 50 observed crystals; whereas at -7[degrees]C, 69% of the 109 observed crystals had threefold symmetry [seeding using dry ice resulted in a similar trend (Yamashita 1973)].
More recently, Westbrook (2011) demonstrated that scalene hexagonal columns orientate with two prismatic faces horizontal (i.e., in the Parry orientation).
We specifically investigate the optical properties of crystals of various sizes that range from trigonal columns with triangular basal faces through scalene columns to hexagonal columns.
The absorption efficiency, however, is consistently lower for trigonal and scalene shapes compared to the hexagonal shaped crystals.