Fever of unknown origin

Disease class: Fever

Also known as

• FUO
• Pyrexia of unknown origin

Fever

Also known as

• Pyrexia
• Febrile response

 

Subtypes

• Fever of unknown origin

Apnoea

Disease class: Respiration disorders

Types

• Sleep apnoea syndromes

Definition

Beau's lines

This is a sign of disease seen in the nails.

Splinter haemorrhage

This is a sign of disease seen in the nails.

Ptosis

Crepitus

Definition

Crepitus means a grating sound. 

It is found in cases of fractured bones when the ends rub together; also, in cases of severe chronic arthritis, by the rubbing together of the dried internal surfaces of the joints.

Source: Black's Medical Dictionary (42nd ed, 2010, ISBN 978-1-4081-0419-4) 

Wheezing

Definition

A popular name applied to the various sounds produced in the chest when the bronchial tubes are narrowed. 

It is applied particularly to the long-drawn breathing of asthma, and to the whistling or purring noises that accompany breathing in cases of bronchitis.

Source: Black's Medical Dictionary (42nd ed, 2010, ISBN 978-1-4081-0419-4)  

Crepitations

Definition

Certain sounds which occur along with the breath sounds, as heard by auscultation, in various diseases of the lungs.

They are signs of the presence of moist exudations in the lungs or in the bronchial tubes, are classified as fine, medium, and coarse crepitations, and resemble the sound made by bursting bubbles of various sizes.

Source: Black's Medical Dictionary (42nd ed, 2010, ISBN 978-1-4081-0419-4)

Stridor

Definition

A noise associated with inspiration due to narrowing of the upper airway, in particular the larynx. 

It is typical of the childhood viral illness, acute laryngotracheobronchitis (croup).

Source: Black's Medical Dictionary (42nd ed, 2010, ISBN 978-1-4081-0419-4)  

Osler's node

Osler's nodes are medical signs.

Features

• Tender
• Erythematous 
• Raised
• Lesions on the palms or soles 

 

Pathophysiology

• Antibody binds to antigen  
• Immune complexes form 
• Complexes are deposited in the tissues  
• Immune complexes trigger tissue inflammation 

 

Causes

• Infective endocarditis
• Systemic lupus erythematosus
• Marantic endocarditis
• Disseminated gonococcal infection
• Distal to infected arterial catheter

 

See also

• Osler's node

Janeway lesion

Janeway lesions are medical signs.

Features

• Non-tender
• Erythematous or haemorrhagic 
• Macular or nodular 
• Lesions on the palms or soles 
• Only a few millimeters in diameter

 

Pathophysiology

• Septic emboli reach the tissues and deposit bacteria
• Micro-abscesses form 
• Marked necrosis and inflammatory infiltrate
• Affects the dermis but not the epidermis

Causes

• Infective endocarditis

See also

• Osler's node

[Neurology] Posturing

Posturing is a medical sign which provides information about central nervous system (CNS) dysfunction.
This is a feature of the motor section of the Glasgow Coma Scale scoring system.

Physiology

The CNS contains many structures which, in earlier mammals, coordinated voluntary and involuntary skeletal muscle activity. In humans, the cerebral cortex has developed to become the master controller of these structures. The cortex and associated structures regulate the passive muscle tone throughout the body. The cerebral cortex is also necessary for fine motor control. It sends signals to the muscles directly through the corticospinal tract.

When there is brain dysfunction, the cortex and corticospinal tract can fail to output neuronal signals. This removes the corticospinal component of muscle tone. However, the subordinate nuclei, which are lower down in the brain, can continue to send signals.

Cross-section of midbrain and cross-section of pons.
Red: red nuclei and rubrospinal tracts
Blue: corticospinal tracts

 

Decorticate posturing

The red nuclei sit in the midbrain. If the dysfunction occurs at a level above the red nuclei, then the red nuclei are able to send signals and modulate the tone of the muscles.

• The flexor muscles in the upper limb draw the upper limbs into flexion.
• The extensor muscles at the neck draw the head into hyperextension.
• The extensor muscles in the legs draw the legs into a hyperextended, internally rotated position.

This is decorticate (no-cortex) posturing. 
GCS score: -3

 

Left: Cross-section of midbrain, red nuclei. Right: decorticate posturing.

 

Decerebrate posturing

The pons (latin: bridge) is in the brainstem situated below the midbrain, above the medulla oblongata, and in front of the cerebellum.

If dysfunction occurs at a level below the red nuclei, the rubrospinal component of passive muscle tone is lost. The pontine nuclei are able to send signals and modulate the tone of the muscles.

• The extensor muscles in the upper limb draw the upper limbs into extension.
• The extensor muscles at the neck draw the head into hyperextension.
• The extensor muscles in the legs draw the legs into a hyperextended, internally rotated position.

This is decerebrate (no-cerebrum) posturing.
GCS score: -4

 

Left: Cross-section of pons. Right: decerebrate posturing.

 

Global hypotonia

If dysfunction occurs at a level below the pontine nuclei, then there are no brain nuclei sending signals to the spinal cord. In the short-term, the global muscle tone will fall, leading to a state of hypotonia.

• All flexor muscles are flaccid and paralysed.
• All extensor muscles are flaccid and paralysed.

GCS score: -5

 

Causes

• Raised intracranial pressure  
• Cerebrovascular infarction (stroke)  
• Intracranial haemorrhage 
• Severe traumatic brain injury 
• Brain, Other CNS & Intracranial Tumours
• Brain herniation 
• Transient posturing called 'fencing response' is often seen in sports, when athletes sustain mild traumatic brain injuries (concussions).

[Neurology] Muscle tone and reflexes

Every muscle in the body has stretch receptors which are stimulated by tension. Signals of high tension are sent up a sensory nerve to the anterior horn of the spinal cord. Here the sensory nerve synapses with a motor nerve which descends back to the muscle and stimulates contraction. The sensory nerve and motor nerve form a reflex arc. This means that an incoming sensation of muscle tension can produce an effector response of muscle contraction as quickly as possible.

The brain sends inhibitory signals down nerves which synapse with the reflex arc. This allows the brain to adjust the sensitivity of this reflex arc, and this is what regulates muscle tension.

Lower motor neuron lesions

When the lower motor neurons are damaged, there is no signal to the muscle fibers. This means that the pathways which produce muscle contraction are inactive and the sarcomeres remain at their maximal length. The muscles remain flaccid and powerless. With time, the muscles will atrophy as there are no signals promoting muscle growth. There will be almost no muscle tension (hypotonia) and no deep tendon reflexes (arreflexia).

These lesions result in flaccid paralysis.

 

Upper motor neuron lesions

Above the anterior horn of the spinal cord, the neurons are known as upper motor neurons. These convey the signal from the brain to the lower motor neurons. When they are damaged, no signal reaches the reflex arc in the spine. This means that no signal for voluntary movement can pass from the brain to the muscle. However the reflex arc is still intact so these muscles are able to maintain high tension. Without the inhibitory signals from the brain, the reflex arc becomes unrestrained and the muscle tone increases (hypertonia). The deep tendon reflexes in the affected limbs are heightened (hyperreflexia).

These lesions result in spastic paralysis. 

Hiccups

Also called hiccoughs.

 

Physiology

A hiccup is a very a common and harmless phenomenon. 

It is a reflex arc from the diaphragm, up the phrenic nerve to the brainstem, then down the vagus nerve to the muscle fibers. It causes involuntary contraction of the diaphragm. The characteristic "hic" or "hup" sounds are caused by an involuntary closure of the glottis as air is drawn past them by the contracting diaphragm. The process usually repeats and may last for minutes or even days. 

The causes and treatments of hiccups are so numerous, that there is no consensus on how exactly the process is coordinated in the brain. The initiation and termination of hiccups are likely mediated by various neurotransmitters.

There is a phylogenetic hypothesis that hiccups are a remnant from the evolutionary history of humans. It may be an earlier pathway of respiration which was used by amphibious ancestors. 

 

Pathology

Even a prolonged bout of hiccups is usually not a sign of underlying disease. 

Hiccups can be triggered by: 

• Excessive air swallowing
• Eating too rapidly
• Intense emotions
• Laughter
• Certain beverages and foods

However, in some cases, it is a useful diagnostic clue. 

• Abdominal pathologies. E.g. subphrenic abscess. In cases with an abdominal infection, the diaphragm can become irritated, stimulating the phrenic nerve. 
• Metabolic disorders. E.g. uraemia. Uraemia may stimulate the initiation of hiccuping in the medulla. 
• Lesions of the central nervous system. E.g. brainstem tumours. 
• Lesions of the vagus nerve. 
• Psychogenic disorders. 
• Drug use. E.g. opioids.  

 

Management

Simple hiccups can often be resolved by simple stimulation of the involved nerves. For example, holding your breath, swallowing water, and other maneuvers may stimulate the glottis. 

[Cardiology] Physical examination

Inspection

• Nail clubbing   
• Osler's node 
• Janeway lesion 

Palpation

• Thrills and heaves 

 

Auscultation 

• Heart murmurs 

[Cardiology] Heart murmurs

This article is about a diagnostic finding from the cardiac examination: murmurs.

 

Auscultation

A cardiac murmur is a disturbance in the blood flow of the heart. It can be heard with a stethoscope. This is called cardiac auscultation.

 

Structural defects

Murmurs often indicate a structural heart defect, particularly when they sound harsh and a thrill is palpable. Structural heart defects are more common in older patients, people with a family history of structural heart disease, or a personal medical history of certain diseases (e.g. rheumatic fever, SLE).

We have to feel the pulse (at the carotid artery) to identify when the heart is in systole (contracting) or diastole (relaxation and filling). A structural defect can produce an audible murmur in either systole, diastole or both, depending on where the defect is and what type of defect it is.

 

Palpation

A thrill is a murmur which can be felt over the turbulence. This is one reason to perform chest wall palpation (feeling the chest wall with the hand).

It can be benign (harmless), particularly when it sounds soft, with no palpable thrill. This is often seen in young children.

 

Accentuation maneuvers

Another important point is accentuation of cardiac murmurs (making them louder). There are 2 important categories of accentuation: breathing, and position.

Some murmurs sound louder when the patient is exhaling (breathing out), but some murmurs sound louder when inhaling (breathing in). This is because the pressure in the thorax (the chest cavity) is relatively low when inhaling (because your ribs rise and diaphragm falls to increase the volume inside the chest). The pressure is relatively high when exhaling (because the thoracic volume is decreasing). When the pressure is low, blood can return to the heart more easily. When the pressure is high, blood can leave the heart more easily.

Some murmurs sound louder when the patient is lying forward, and some sound louder when the patient is lying on the left side of their body. This is because the position of the patient is bringing the diseased valve closer to the surface of the chest wall, so the sound of the turbulence is closer to the stethoscope.

 

Radiation

It is also important to listen over the carotid arteries, and under the left axilla (armpit) with a stethoscope. This is because some murmurs will classically radiate (spread) to the carotids, the back, or the axilla. This is because of the direction of the turbulent jet of blood through the valve. In mitral incompetency (back flow of blood through the mitral valve during systole), there is a systolic murmur. In aortic stenosis (narrowed forward flow through the aortic valve during systole), there is a systolic murmur. How do we tell them apart easily?

In mitral insufficiency (also called mitral incompetence, mitral regurgitation), the jet of blood which is regurgitating is heading towards the left axilla or the left scapula (shoulder blade), so a sound wave is pushed in that direction, and the murmur may be audible at these locations.

In aortic stenosis, the heart is pushing blood upwards through a narrow aortic valve so it can flow through the aorta to reach the body. A sound wave is pushed upwards towards the neck, and may be audible through the carotid arteries, which branch upwards from the aorta.

 

Diagrams

The diagrams below show which defects may cause a systolic or diastolic murmur.

 

Key

Arrows: direction of blood flow
Cylinder: major vessel
Thickened circle: stenotic (narrowed) valve
Backward arrow: regurgitant flow, through incompetent valve
Cloud: septal defect

Murmurs heard during systole

Murmurs heard during diastole

 

Worked example

A patient is brought to the hospital after syncope (fainting). She is in her 60s. Her father had his aortic valve surgically replaced in his 40s. When listening to the chest there is a harsh, crescendo-descrendo, systolic, murmur. It is loudest over the aortic valve. The sound can also be heard over the carotid arteries.

The answer here is aortic stenosis. This patient and her father both had bicuspid aortic valve. This is a congenital abnormality in which the aortic valve has only 2 cusps instead of 3. This means that blood flow through the aortic valve is turbulent, and over many years, the valve can become calcified and stenotic (narrowed). These patients often require a valve replacement when they are in their 40s.

If they are young, it is best to use a mechanical valve replacement. Anti-coagulation is necessary because blood clots will form on the artificial valve more easily than a natural valve. If the patient is old enough, you can use a biological prosthetic valve, since they may die before it degrades.

Nail clubbing