Cranial Nerves PDF

1. 2. 1. To muscles of mastication  2. To mylohyoid 3. To anterior belly of the digastric 4. To tensor tympani & tensor veli palatini 3. **Which nerve innervates the posterior belly of the digastric?** Facial Nerve (CN VII) 4....

1. 2. 1. To muscles of mastication  2. To mylohyoid 3. To anterior belly of the digastric 4. To tensor tympani & tensor veli palatini 3. **Which nerve innervates the posterior belly of the digastric?** Facial Nerve (CN VII) 4. 5. 1\) Meningeal branch **6.** **Upper motor neuron (UMN)** lesions affect the facial nerve, [only the lower face] on the contralateral side is affected. This happens because the upper facial muscles receive bilateral innervation from both hemispheres, so the unaffected hemisphere can still supply the forehead muscles on both sides. **7. Lower motor neuron (LMN)** lesion affects the [entire ipsilateral side of the face], including both the upper and lower face. **8**. The corneal reflex involves both the trigeminal nerve (cranial nerve V) and the facial nerve (cranial nerve VII). **9.** The **pupillary light reflex** involves three nerves: **10**. **Three main cranial nerves** associated with taste 1\) Anterior 2/3 of the tongue: Facial nerve (CN VII) 2\) Posterior 1/3 of the tongue: Glossopharyngeal nerve (CN IX) 3\) epiglottis and pharynx: Vagus nerve (CN X) **11.** **Extraocular muscles** and their innervations: **Oculomotor Nerve (Cranial Nerve III)** innervates most of the extraocular muscles except two. \- Superior rectus: Elevates the eye \- Inferior rectus: Depresses the eye \- Medial rectus: Moves the eye medially (adduction) \- Inferior oblique: Elevates and extorts the eye **Exceptions:** - - **12. Pupillary Size and Reaction to Light:** When pupils do not react to light, it may suggest optic nerve damage. Dilation due to drug use may also affect pupillary response to light. **Test of Accommodation:** **Accommodation** is the process where the eye adjusts its optical power to focus on objects at varying distances. **Cranial nerves involved:** 1. 2. 3. **13. Nystagmus** - eyes move rapidly and uncontrollably. The side to side (horizontal nystagmus) one is the most common nystagmus. **Lid lag-** Static situation in which the upper eyelid is higher than normal with the globe in downgazehttps://lh7-rt.googleusercontent.com/docsz/AD\_4nXexX8C6CiH5SMxgKXUvJFUhQ44eUkVoI9XpkH1ZBkYaloe9ZTKiB\_aBrQ0pLNFRs5HtpuIpbjuE3wcCcFkBoYHaxFj-Wxu3uSbYS1GKf9hVaPz4HSV9VWyX6kaOv2gtvLDIdvzyFHNIcUpvzppsnjA?key=9H6wCcdriNpZ5P-WQaF8Pipa **3 nerves involved with taste sensation** **Anterior ⅔**: Facial Nerve (Chorda Tympani branch). **Posterior ⅓**: Glossopharyngeal Nerve. **Below posterior ⅓ portion → Epiglottis and pharynx**: Vagus Nerve. **Gag reflex**: - The **afferent (sensory)** component of the gag reflex is mediated by the **Glossopharyngeal Nerve (Cranial Nerve IX)**. **Sensorineural Hearing Loss** - **Problem Location**: Inner ear (cochlea) or auditory nerve. - **Air conduction with tuning fork**: Sound is reduced but **still heard better through air conduction** than bone conduction (**AC \> BC**). - **Example Conditions**: - **Microtia** (small or underdeveloped external ear) can indicate sensorineural issues if the cochlea or auditory nerve is affected. - **Pad ear** (if inner ear or nerve is damaged). **Conductive Hearing Loss** - **Problem Location**: Outer or middle ear (e.g., ear canal, eardrum, ossicles). - **Air conduction with tuning fork**: Sound is weaker through air because it's blocked, but bone conduction is normal or better (**BC \> AC**). - **Example Conditions**: - **Pad ear** (if wax blocks sound in the ear canal). - Structural issues like **microtia** causing a blocked ear canal or missing eardrum. Orthognathic surgery = surgery that corrects the relationship of maxillary and mandibular jaws Cocaine is a vasoconstrictor = ischemia and necrosis of the cartilage leading to septal perforation **14. Sphenoid sinus** cannot be palpated because it's **located too deep** - ONLY sinus that cannot be examined clinically **15.** A deviation of the tongue toward the affected (damaged) side indicates an issue with the hypoglossal nerve (Cranial Nerve XII). **Paralysis causes deviation to the weak side**. When the patient tries to protrude their tongue, it deviates toward the side of the lesion.  **Left side is affected ** **16. ** **TMJ dislocation** - The condylar head (part of the jawbone) moves **anteriorly and superiorly** beyond the articular eminence (bony structure of the TMJ) and patient **cannot reposition** on their own **TMJ subluxation** - The condylar head also moves **anteriorly and superiorly**, but the patient **can reposition** the jaw themselves. **17. TMJ Arthritis:** **Crepitus** is often heard in the joint during mandibular motion.  - very rare to have with MPDS = (myofascial pain) **18**. **Trismus** refers to a restricted range of motion in opening the mouth, often due to spasms, inflammation, trauma, or fibrosis of the masticatory muscles. Severe trismus can prevent a patient from fully opening their mouth. **19. Ankylosis of the temporomandibular joint (TMJ)** can lead to severe trismus. Ankylosis is the abnormal fusion or stiffening of the condylar head of the mandible to the base of the skull (usually involving the temporal bone). This fusion restricts or completely prevents movement at the TMJ, resulting in an inability to open the mouth normally. **20. Deviation of mandible on mouth while opening:** Observe the opening pattern for deviation. The mandible often deviates [toward the affected side] during opening **Maximum Incisal Opening (MIO)**: - The distance between your upper and lower front teeth when you open your mouth fully. - **Normal range**: 40--55 mm. **Quick Check (Using Fingers)**: - **Three fingers fit**: Normal opening. - **Two fingers fit**: Slightly reduced opening, still functional. - **One finger fits**: Severely reduced opening, likely a problem with the jaw or muscles. **How to detect any joint tenderness, clicks or crepitus, including**  **movement of the jaw joint (TMJ)** and **capsular tenderness** (pain in the TMJ capsule) - Place your **little finger** inside the ear canal (**external auditory meatus**). - As the patient moves their jaw, you can feel the **posterior (medial) pole of the condylar head** with the fingertip. https://lh7-rt.googleusercontent.com/docsz/AD\_4nXcl1-d3LT0fwrsvMsLIxYVzCOCvBEvJ2WmrlVUoziwBNI2OiAyMV93tnalgxb9EvuqnxoE4Rfsf1m29Tgk7gyiXwVk44UQCIyLB\_SWOHFHX\_L91-ntkvHOUW0PRL1WsSadIg5A4gCF-4us22p\_jGbY?key=9H6wCcdriNpZ5P-WQaF8Pipa **21. Muscles of Mastication:** Masseter, Temporalis, Medial Pterygoid, Lateral Pterygoid  **22. Strap Muscles of the Neck:** Sternohyoid muscle, Thyrohyoid muscle, Omohyoid muscle, Sternothyroid muscle, Platysma muscle **23. Cricoid cartilage** is actually the **only complete ring** among the laryngeal cartilages. **Cricoid Cartilage: A ring-shaped cartilage in your neck that surrounds the trachea (windpipe) and forms the lowest part of the larynx (voice box).** 1. **Connections**: - **Top (Superior Border)**: Linked to the **thyroid cartilage** (Adam\'s apple area) through the **cricothyroid ligament/membrane**. - **Bottom (Inferior Border)**: Attached to the first ring of the trachea via the **cricotracheal ligament**. 2. **Important Procedures**: - **Cricothyrotomy (or Cricothyroidotomy)**: - A quick emergency procedure to create an airway. - Involves making an incision in the **cricothyroid membrane**. - **Cricoidectomy**: - Surgical removal (partial or total) of the cricoid cartilage. - Rarely done because it\'s not a common procedure. **24.** The **2nd and 3rd tracheal rings** are considered the ideal location for a **tracheostomy**. **25.** **\"Virchow\'s node\"**- left supraclavicular often a clue to abdominal or thoracic malignancy. **26.** **Thyroid Gland:** 1. **What is it?** - A gland in your neck divided into two parts (lobes) connected by a bridge (isthmus). 2. **Where is it?** - Sits below the muscles in your neck and wraps around the windpipe (trachea) near the cricoid cartilage. 3. **What does it do?** - Produces hormones that control your metabolism (how your body uses energy). **Parathyroid Glands:** 1. **What are they?** - Small glands located behind the thyroid gland. Most people have four of them. 2. **Where are they?** - Two are at the top (superior) and two at the bottom (inferior) of the thyroid gland. 3. **What do they do?** - Control calcium levels in your blood, which is important for bones, muscles, and nerves.