1st Cranial nerve – Olfactory nerve Lesions

Definition: An olfactory lesion is a pathological process negatively affecting the function of the first cranial nerve. Olfactory lesions can be sub-divided into the following categories: a) anosmia: inability to appreciate qualitative olfactory sensations, b) partial anosmia: the ability to appreciate some but not all odorants, c) microsmia or hyposmia: reduced sensitivity to odorants d) […]

2nd Cranial nerve – Optic nerve lesions

Definition: A pathological process involving the optic nerve. Causes: Pathological processes affecting the visual field. Depending on the site of the lesion, a pathological process affecting the second cranial nerve can have various presentations: Monocular blindness: Lesions of one eye or optic nerve such as in multiple sclerosis or giant cell arteritis. Bilateral blindness: Methyl […]

3rd Cranial nerve – Oculomotor nerve palsies

Definition: Oculomotor (III) nerve lesions are pathological processes which negatively affect the nerve’s function. Causes: The exact aetiology of most cases of oculomotor nerve palsies is idiopathic. There is a hereditary component to this condition, where the usual causative factor is either an aplasia or hypoplasia of one or more of the muscles supplied by […]

4th Cranial nerve – Trochlear nerve lesions

Definition: Trochlear (IV) nerve lesions are abnormal pathological processes which negatively affect the nerve’s function. Causes: As with oculomotor nerve palsies, trochlear nerve palsies can be broadly divided into congenital and acquired. Isolated acquired trochlear nerve palsies are difficult to diagnose, and are therefore often idiopathic. Below is a list of acquired cranial nerve IV […]

5th Cranial nerve – Trigeminal nerve lesions

Definition: A trigeminal nerve lesion describes any pathological process, with the potential to negatively affect the nerve’s function. This definition encompasses: trigeminal neuralgia, tic douloureux (prospalgia, suicide disease, Fothergill’s disease). The 5th nerve has three divisions. They consist of the ophthalmic, maxillary, and mandibular nerves. The sensory aspect of the trigeminal supplies; sense of touch,pain […]

6th Cranial Nerve – Abducens nerve lesions

Definition: Abducens nerve (cranial nerve VI) lesions are pathological processes which negatively affect the nerve function. Causes: The exact aetiology of most of the cases of abducens nerve palsies is idiopathic. Research suggests that there may be a hereditary component to this condition. Broadly speaking, this condition can be divided into acquired and inherited. Below […]

7th Cranial Nerve – Facial nerve lesions – Bell’s Palsy

Definition: Facial hemiparesis as a result of a lesion to the facial nerve: cranial nerve VII. Examination: Although the true aetiology of facial nerve palsy also known as Bell’s palsy is not fully understood a number of well postulated theories may be considered; these include: Viral infection such as HSV-I (Herpes Simplex Type-) being reactivated […]

8th Cranial Nerve – Vestibulocochlear nerve Lesions

Definition: The vestibulocochlear nerve, cranial nerve VIII, is responsible for sound and equilibrium. A lesion affecting this nerve is a pathological process with the potential to negatively affect its function. Causes: There are numerous possible mechanisms by which the vestibulocochlear nerve can be injured. The resulting signs and symptoms will vary depending on whether the […]

9th Cranial Nerve – Glossopharyngeal nerve Lesions

Definition: A pathological process involving the ninth cranial nerve. Causes: The common causes are; brainstem lesions, trauma, cerebellopotine angle and neck tumours, polio, and Guillain Barré  syndrome.   Examination: Unilateral lesions to the ninth cranial nerve do not cause any deficit due to the bilateral corticobulbar connections. Bilateral lesions result in pseudobulbar palsy. Glossopharyngeal nerve lesions […]

10th Cranial Nerve – Vagus Nerve Lesions

Definition: Tenth (X) cranial nerve palsies are pathological processes which negatively affect the nerve’s function. Causes: An isolated palsy of the Vagus nerve is extremely rare. Causes include: trauma brainstem lesions tumours in the cerebellopontine angle Gullain-Barr syndrome space occupying lesions dissecting aortic aneyurism Examination: Vagus nerve lesions commonly result in palatal and pharyngeal paralysis; […]

11th Cranial Nerve – Accessory Nerve Lesions

Definition: A pathological process affecting the eleventh cranial nerve. Causes: Supranuclear lesions of the accessory nerve result in mild, usually transient, dysfunction of function of the sternocleidomastoid and trapezius muscles, due to the bilateral innervation. In the spinal cord the nuclei of the eleventh cranial nerve can be affected by amyotrophic lateral sclerosis (ALS), syringomyelia, […]

12th Cranial Nerve – Lesions of the Hypoglossal nerve

Definition: Hypoglossal nerve lesions are pathological processes which negatively affect the nerve’s function. Lesions affecting cranial nerve XII are uncommon. Causes: Causes of isolated Hypoglossal nerve palsies are rare but include: malignancies cerebrovascular accidents space occupying lesions head and neck trauma infection certain autoimmune pathologies Examination:  Lesions affecting cranial nerve XII produces characteristic clinical manifestations, […]

Upper Motor Neuron Lesions

Definition: This implies lesions of the corticospinal tracts. These are made up of the neurones which control voluntary movement. A lesion affecting these neurones anywhere from their origin (where their cell bodies reside) in the motor cortex or the pre-central gyrus ( the region between the frontal and parietal lobes) and throughout the course of […]

Gag Throat Reflex

Definition: The gag reflex evaluates the integrity of Cranial nerves IX and X (The glossopharyngeal and vagus nerves) Test procedure: Using a long handle swab stick (orange swab) gently and briskly touch the pharyngeal wall behind the pillars of the fauces. Test findings: A positive gag reflex will produce a non symmetrical elevation of the […]