The most common cause of homonymous hemianopia (HH) is a stroke. In this condition there is bitemporal field loss. Lesions posterior to the optic chiasm, in the brain parenchyma are most likely to be the cause of the HH. In this case the retention of central vision indicates that the area of injury may be in the occipital cortex, sparing the occipital pole. The occipital pole receives sensory fibres from the macular, and has a dual blood supply protecting it from total infarction. Lesions of the optic tract can be ruled out as these cause total vision loss in the affected eye. Parietal or temporal nerve lesions cause affect the inferior and superior parts of the visual field respectively causing homonymous quadrantinopias.

The boy is most likely to have sustained an injury to his brachial plexus as a result of upward traction of his arm for an extended period of time. We can rule out the topmost nerve roots of the brachial plexus, C6 and C7 as these supply the larger muscles of the arm responsible for moving the shoulder, the elbow and the wrist. The anatomical structure affected is therefore the T1 nerve root which is responsible for movement of the muscles in the hand. This type of injury is called a Klumpke’s Palsy, which is the result of a hyper-abducted trauma to the arm, damaging the C8 and T1 nerve roots. While the radial and ulnar nerve also innervate the hand, the history given points to Klumpke’s palsy as the best explanation for this mechanism of injury.

Cranial nerve VI, also known as the abducent nerve, innervates the ipsilateral lateral rectus (LR), which functions to abduct the ipsilateral eye. Patients usually present with an isolated abduction deficit, binocular horizontal diplopia, worse in the distance, and esotropia in primary gaze. Patients also may present with a head-turn to maintain binocularity and binocular fusion and to minimize diplopiaExamination for a sixth nerve palsy involves documenting the presence or absence of papilledema, examining the ocular motility, evaluating the eyelids and pupils, and excluding involvement of other cranial nerves (e.g., V, VII, VIII).

Successful administration of median nerve block can be confirmed by the inability to abduct the thumb. The median nerve supplies all the muscles in the anterior compartment of the forearm, apart from the flexor carpi ulnaris and the flexor digitorum profundus to the outer two fingers: so these two fingers can still be flexed. There is a sensory loss to the thumb, index, middle and half of the ring fingers. Absence of thumb abduction due to paralysis of abductor pollicis brevis is a good test for median nerve paralysis.Other options:- The radial nerve supplies the extensors -hence wrist drop does not occur in this scenario. – The ulnar nerve supplies the skin of the ulnar side of the hand. Hence anaesthesia will not affect this area. – The ulnar nerve also supplies the interossei muscles of the hand, which affect abduction and adduction of the fingers.

The azygos lobe is usually well seen on the chest radiograph, where it is limited by the azygos fissure, a fine, convex (relative to the mediastinum) line that crosses the apex of the right lung.

Endothoracic fascia: the connective tissue (fascia) that is between the costal parietal pleura and the inner wall of the chest wall. Costomediastinal recess: the point where the costal pleura becomes mediastinal pleura. Costodiaphragmatic recess: is the lowest point of the pleural sac where the costal pleura becomes diaphragmatic pleura. Cupola: the part of the parietal pleura that extends above the first rib level into the root of the neck. Costocervical recess: this is a made-up term. Peritracheal fascia: a layer of connective tissue that invests the trachea.

The inferior alveolar nerve supplies all the teeth of the respective hemimandible. It transverses the inferior alveolar canal and is a branch of the trigeminal nerve’s mandibular division. Therefore, in this case, the teeth of the right hemimandible will be numb.

Cranial nerve II (CN II or optic nerve) runs along the midline of the ventral surface of the brain and conveys visual information from the retina of each eye to the corresponding region of the primary visual cortex. The right half of the visual field of both eyes is processed by the left half of the retina, while the right half of the retina processes the left half of the visual field. These retinal ganglion cells project myelinated axons, carrying CN II sensory afferent fibres, through the optic chiasm, where optic nerve fibres from the nasal half of each retina decussate to the contralateral side of the brain for processing. After passing through the optic chiasm, the optic nerve becomes the optic tract that synapses to the lateral geniculate nucleus (LGN) of the thalamus and subsequently projects optic radiations to the primary visual cortex (V1) of the occipital lobe. The optic tract also projects to the superior colliculus, pretectal nuclei, and suprachiasmatic nuclei. This part of the optic pathway serves the important light reflex.Due to the anatomical location of the optic chiasm superior to the pituitary gland, a suprasellar extension of a pituitary macroadenoma will lead to compression of the optic nerve fibres decussating at the optic chiasm. Impingement of these nerves prevents visual information from the temporal visual fields of each eye from reaching the processing centres in the brain, leading to peripheral vision loss

Among the given options, the inability to grip a sheet of paper between his fingers when the hand is placed flat on the table is the feature of ulnar nerve injury. Rationale:The ulnar nerve (usually) supplies sensation to the skin of the fifth and the ulnar side of the fourth finger, front and back. Following the injury of the nerve, the following functions are impaired:- There is a sympathetic interruption, with the absence of sweating in the affected area. – The thenar muscles are supplied by the median nerve and are therefore spared. – The ulnar nerve also supplies the muscles of the hypothenar eminence. – Although the ring and little fingers are held in the clawed position when the nerve is injured at the wrist, a high lesion paralyses the long flexors to these two fingers and results in the loss of this sign. The test for paralysis of the palmar interossei, supplied by the ulnar nerve, is the inability to adduct the fingers and thus to be unable to grip a sheet of paper between them.

The recurrent laryngeal nerve (RLN) innervates all of the intrinsic muscles of the larynx except for the cricothyroid muscle, which is innervated by the superior laryngeal nerve (SLN).Patients with unilateral vocal fold paralysis present with postoperative hoarseness or breathiness. The presentation is often subacute. At first, the vocal fold usually remains in the paramedian position, creating a fairly normal voice. Definite vocal changes may not manifest for days to weeks. The paralyzed vocal fold atrophies, causing the voice to worsen. Other potential sequelae of unilateral vocal-fold paralysis are dysphagia and aspiration.Bilateral vocal-fold paralysis may occur after total thyroidectomy, and it usually manifests immediately after extubation. Both vocal folds remain in the paramedian position, causing partial airway obstruction. Patients with bilateral vocal-fold paralysis may present with biphasic stridor, respiratory distress, or both. On occasion, the airway is sufficient in the immediate postoperative period despite the paralyzed vocal folds. At follow-up, such patients may present with dyspnoea or stridor with exertion.