Olfactory Nerve (CN I) and Smell

Background

• CN I/Olfactory nerve is the shortest cranial nerve and consists of special unmyelinated sensory nerves responsible for sense of smell
  • They are, however, covered in Schwann cells

The olfactory pathway

• Odourant molecules can enter your system via your nose or mouth and nasopharynx.
• They reach an area called the olfactory mucosa in the nasal cavity
  • Here, they come into contact with the olfactory receptor neurons and activate receptors to initiate an action potential
    • The axons of these cells traverse the cribiform plate of the ethmoid bone at the roof of the nasal cavity and become the olfactory bulb.
  • In the bulb, these neurons communicate with specialised mitral cells at the synaptic glomeruli.  These then pass posteriorly into the olfactory tract
    • This runs along the inferior aspect of the frontal lobe.  At the anterior perforated substance, the tract divides into medial and lateral stria.
      • Medial stria connects to the limbic system and communicates with the contralateral olfactory medial stria
      • Lateral stria continues to the primary olfactory cortex in the temporal lobe, which goes on to communicate further with the limbic system (amygdala, piriform cortex and olfactory tubercle) and orbitofrontal cortex.
• Note
  • CN I is covered by pia and arachnoid layers (i.e. continuation of the brain).  It does also not join with the brainstem.
  • The olfactory nerve is capable of regeneration.

Olfactory Dysfunction (Anosmia)

• Temporary anosmia is not uncommon in local conditions of the nose e.g. infection.
• Other causes of anosmia/abnormal sensation of smell include
  • Tumours in the olfactory groove (meningioma)
  • Head injury- damage to the cribiform plate may cause damage to the olfactory receptors
  • Neurodegenerative disease e.g. Parkinson’s Disease, Huntington’s and Alzheimer’s disease
  • Genetic conditions e.g. Kallman Syndrome, Primary ciliary dyskinesia, Foster Kennedy Syndrome
  • Partial epilepsy (pre- and post-ictal)

Testing CN I

• Ask the patient if they have noticed a change in their sense of smell.
• A more formal assessment of smell can involve using common smells

Slipped Upper Femoral Epiphysis

Background

• One of the most common adolescent hip problems (around 10/100,000 children per year)
  • The epiphysis usually slips posteriorly relative to the diaphysis of the femur
• Most common in boys and occurs usually around the growth spurt in adolescence (mean age 13)
  • More common in overweight children; left hip slightly more prevalent
  • Whilst weight and mechanical factors (as well as others e.g. hypothyroidism; hypopituitarism; radiation treatment) may play a role, SUFE represents an underlying instability of the proximal growth plate- the exact cause of which is unknown

Classification

• The most important classification is whether the joint is
  • Stable (90%) i.e. the patient is still able to weight bear (function relatively unimpaired)
  • Unstable (10%) the patient is unable to weight bear- requires urgent management
• Other classifications include
  • time-based i.e. acute (symptoms for < 3 weeks); chronic and acute on chronic
  • Southwick angle classification (measurement of the difference between both hips in the femoral head-shaft angle on the frog radiograph)
    • Mild <30°; Moderate 30-50° and severe >50°
  • Grading by degree of slippage
    • I (Up to a third); II (up to a half); III (more than half)

Presentation

• Most commonly presents with hip and/or groin pain
  • Often an acute event but may present but can have had mild symptoms preceding this
  • Can present as radiated knee pain
  • Worse on movement/weight bearing
  • May cause antalgic gait
  • May limit hip movement- particularly internal rotation and abduction (indeed the leg may rest in external rotation/adduction)
• Differential
  • Perthes disease
  • Septic arthritis
  • Developmental dysplasia
  • Synovitis

Investigation

• X-rays
  • An x-ray of the pelvis will usually detect a SUFE
    • Trethowan’s sign
      • Klein’s line (the line drawn up the lateral edge of the neck of the femur) should intersect the femoral head. It fails to do so in SUFE due to slip.
    • You may also see widening of the growth plate (epiphysiolysis) and blurring of the proximal femoral metaphysis (overlapping of the metaphysis and displaced epiphysis)
• Occasionally, where diagnosis is in doubt, a CT or MRI may help confirm the diagnosis

Management

• Surgical management of the affected side
  • Percutaneous fixation with cannulated screw(s)
• There is some controversy as to whether to fix the other side also (bilateral in up to 20% of cases)- currently not recommended
• Without fixation, particularly in unstable cases, there is a risk of osteoarthritis; chondrolysis (breakdown of cartilage and subsequent bony degeration/damage) and avascular necrosis of the femoral head

Scoliosis

Abnormal curvature of the spine in the coronal plane (>10°).

Background/epidemiology

• Scoliosis <10° is not abnormal (considered a normal variation)
  • Around half of patients with AIS (adolescent idiopathic scoliosis- most common form) develop a curvature >70°
• It is estimated to affect 2-3% of the population; 80% is idiopathic
• The most common type is adolescent idiopathic scoliosis (affects between 0.5 and 3% of people, most commonly between the ages 12-14, and, in IAS, is much more common in females (90%)
  • Other common types include
    • Juvenile idiopathic scoliosis (aged between 3 and 10; more common in females; likely to progress/require surgery due to curvature presenting prior to growth spurt at puberty)
    • Infantile idiopathic scoliosis (< age 3; more common in males)
    • Congenital idiopathic scoliosis
    • Neuromuscular and Pathologic Scoliosis (Secondary conditions)
• In older children, curvature is usually to the right.  In infants, left sided curvature is more common.
• As curvature progresses, vertebral bodies rotate towards convexity and spinous processes away from convexity.  In severe cases, this can impair cardiorespiratory function.

Presentation

• May be asymptomatic and detected by chance- note that screening is not routinely offered in the UK (some patients also have a family history)
• Usually present with back (thoracic) pain
• On examination (see back examination)
  • Shoulders/waistline may not be level and/or ribs/scapulae may be more prominent in certain areas
  • Note that the hip usually protrudes on the concave side
  • Adam’s Test
    • Ask the patient to bend forward- a fixed scoliosis becomes more prominent
  • It is important also to look for leg length inequality; any focal neurology (change in reflexes) or any signs of congenital/hereditary conditions e.g. midline skin defects, cafe au lait spots.

Investigations

• XR spine
  • Calculating the Cobb angle (between the uppermost and lowermost vertebra of the primary curvature seen on erect AP XR) is important in deciding management/prognosis

Management

• Exercises
  • Back exercises have very little effect on curvature but can maintain mobility/range of movement and may improve pain
• Bracing
  • Used mainly for curvatures between 20° and 40°, which are well balanced (i.e. have a compensatory secondary curve), and in patients who are growing (in puberty) in which a brace may halt the progression and occasionally improve the deformity
  • Usually not definitive- used mainly to maintain curvature stability in younger patients until adolescence when operative management may be more suitable
• Surgery
  • Spinal fixation (posterior spinal fusion most common) can be used in patients with a curvature of >40°
    • rare but carries risk of neurological complications

Kyphosis and Scheuermann’s disease

Kyphosis is the apical-dorsal curvature of the spine in the sagittal plane (i.e. curves away from the body).  There is normal thoracic kyphosis of around 20-40°.  Abnormal kyphosis is a curvature (measured as Cobb’s angle (between T2-T12)) of >45°.

Background/Aetiology

• Pathological kyphosis most commonly occurs in the thoracic spine although rarely can occur elsewhere in the spine.
• It is not uncommon amongst the elderly population (occurs in around 20-30% of patients >65) and is more common in women
• Risk factors include
  • Osteoporosis; vertebral (wedge) fractures and degenerative disc disease
  • Problems with proprioception; poor posture; spinal muscle weakness/attenuation
  • Other causes include trauma; ankylosing spondylysis and other arthritides; and rarely neoplasms and infections
• Kyphosis can impair physical functioning; quality of life and mortality directly and indirectly
  • Increased risk of vertebral fracture
  • May affect balance and likelihood of falls
  • Decline in gait speed/mobility
  • In some cases, can impair pulmonary, GI and gynaecological function

Presentation

• Most patients are asymptomatic and kyphosis is purely aesthetic
• Some may present with back pain
• On examination, there is usually a thoracic kyphosis and there may also be compensatory lumber hyperlordosis
  • Tight hamstrings/difficulty with straight leg raise may also be present
• Rare but important features include those of myelopathy i.e. neurological problems (including pain/altered sensation, weakness, altered tone/reflexes, problems with gait etc)
• Indications for surgical management (note not absolute)
  • Neurological deficits
  • Kyphosis >70° (no pain) or >65° with pain
  • Loss of anterior vertebral height >50%

Management

• For purely postural related kyphosis, exercises and education about posture may benefit patient symptoms (may not entirely relieve kyphosis)
• Surgical management is reserved only for severe cases
  • Smith-Peterson osteotomy, pedicle subtraction and vertebral column resection can all be options for corrections
  • Anterior release spinal fusion may also be used in Scheuermann’s disease/severe cases

Scheuermann’s disease

• In children and adolescents, abnormal kyphosis can occur as what is thought to be the result of a genetic defect causing collapse of the vertebrae
  • A family history is common
  • Patients
• Classically defined as anterior wedging of >5° across three consecutive vertebrae, and is different from postural kyphosis by the rigidity of the kyphosis (not corrected by hyperextension)