Dorsal Interosseous Muscles

During the task, subject maintained the first dorsal interosseous muscle while having their EEG recorded. Visual stimuli have been ignored. 

A useful clinical maneuver to assess the state of the ulnar nerve is the Froment s test . The patient is asked to pinch a sheet of paper between thumb and index finger. In case of overt ulnar neuropathy, the patient grasps the paper by flexing the thumb (activation of the median-innervated flexor pollicis longus as a compensation for the weakness of dorsal interosseous muscles) (see Sect. 8.5.4.3). In patients with cubital tunnel syndrome, palpation of the ulnar nerve at the cubital tunnel may be painful and may reproduce symptoms. 

Finally, the interosseous muscles (four dorsal and three plantar) lie in the fourth and deepest layer, within the intermetatarsal spaces (Fig. 17.3d). The dorsal interosseous muscles arise from the adjacent facing surfaces of the metatarsal shafts and insert into the lateral surface of the base of the proximal phalanx of the toes (except for the first one which inserts onto the medial surface of the second toe). The plantar interosseous muscles are found immediately plantar to the dorsal ones. They arise from... 

As a rule, an accurate and systematic US examination of the dorsal muscles of the forearm should begin at the level of the wrist, where their individual tendons are easily distinguished within the six compartments. Then, US scanning should be performed by shifting the transducer upward to depict the myotendinous junction and the belly of the appropriate muscle to be evaluated. This retrograde technique is particularly helpful, even for the experienced examiner, to increase confidence on establishing the identity of the forearm muscles. At the middle third of the dorsal forearm, the muscle bellies of the superficial and deep layers are divided by a transverse hyperechoic septum (Fig. 9.9). More deeply, the hyperechoic straight appearance of the interosseous membrane and the profile of the radial and ulnar shafts separate the dorsal compartment from the volar compartment (Fig. 9.9). 

---