Category: Adam P. Smith, MD


Cerebral Aneurysms

Cerebral aneurysms are a weakness in the blood vessel’s wall that leads to a small focal dilation.  The etiology is debated, but they most probably start as a congenital wall weakness and later enlarge and dilate; changing size and morphology as we age.  The true prevalence of aneurysms in the general population is difficult to predict, but a reasonable estimate is ~5%.  15-20% of patients with an aneurysm will actually have multiple aneurysms.  Risk factors over time for aneurysmal enlargement include older age, smoking, hypertension, atherosclerosis, amphetamine use, head injury, heavy alcohol consumption, blood infections, and low estrogen after menopause.  Congenital risk factors include connective tissue disorders, polycystic kidney disease, coarctation of the aorta, and family history of aneurysms.  Aneurysms also have been found to occur in predictable locations such as branches off blood vessels.  Anterior communicating artery and posterior communicating artery aneurysms are the most common.

Aneurysms may either be identified after rupture (usually presenting as a subarachnoid hemorrhage or intracerebral hemorrhage), after surveillance imaging for a new neurologic deficit or headaches, or incidentally on imaging for an unrelated issue.  Ruptured aneurysms are the most common cause of spontaneous subarachnoid hemorrhage.  Usually the aneurysm temporarily thromboses following the initial bleed, however re-hemorrhage may occur.  The initial treatment for subarachnoid hemorrhage is to stabilize the patient in an intensive care unit followed by surgical treatment of the aneurysm.

A noncontrast computed tomography (CT) scan is useful in determining if a subarachnoid hemorrhage has occurred and may identify larger aneurysms.  If the clinical findings suggest a bleed but the CT scan appears negative, a lumbar puncture may be performed to identify red blood cells or xanthrochromia in the cerebral spinal fluid.  If an aneurysm is suspected, ruptured or unruptured, a CT angiogram or magnetic resonance angiogram are also useful tests to identify possible intracranial aneurysms.  However a dedicated four vessel cerebral angiogram is the gold standard for diagnosis.

Great debate exists as to the treatment of unruptured cerebral aneurysms.  As a result there have been a number of efforts to determine the natural history of aneurysms in relation to morbidity and mortality, patient age, aneurysm size, and aneurysm location.  The International Study of Unruptured Intracranial Aneurysms (ISUIA) was a two part study attempting to evaluate these issues.  Based on size and location, aneurysms smaller than 7mm appear to have a very low risk of rupture and it is not until they are larger than ~13mm that significant risk or rupture exists, unless the aneurysm is in the posterior circulation.  If the aneurysm is a posterior communicating artery aneurysm or in the posterior circulation, aneurysms larger than 7mm pose a fairly significant risk of rupture.  Of course these are not steadfast rules.  Any aneurysm may rupture at any time, and patients should be counseled regarding their specific risk factors for rupture and desire for prophylactic surgery.  A young patient with a 3mm aneurysm who is a smoker has a different risk profile to an older healthy patient with same size aneurysm.  Any patient with an aneurysm should be evaluated by a neurosurgeon.

There have been no identified conservative management strategies for aneurysm treatment other than changing modifiable risk factors.  Surgery is the only definitive treatment.  Surgery may be performed as an open procedure where a metal clip is placed on the aneurysm or as an endovascular procedure where small metal coils are placed inside the aneurysm.  In either strategy, the aneurysm dome is blocked so that blood cannot enter and the vessel wall repairs with time.  There are advantages and disadvantages to either procedure.  A large study called the International Subarachnoid Aneurysm Trial (ISAT) was reported in 2002 to compare the two treatments.  It appears that either treatment may successfully treat aneurysms.  However, the aneurysm location, morphology, and patient preference are the key features that should determine whether an aneurysm is microsurgically clipped or endovascularily coiled.

For and evaluation please call The Neurosurgery Center of Colorado at 303-481-0035 and make an appointment with Adam P. Smith, MD.

 

Peripheral nerve disorders comprise a wide variety of pathologies.  Most prevalent are compressive entrapments, with carpal tunnel syndrome and cubital tunnel syndrome being some of the most common.  A peripheral nerve may be compressed at any point from where the nerve roots exit the spinal cord to their insertion into muscles.  However, common points of compression exist.  The key in diagnosing entrapment location is knowing the innervation patterns of each nerve, the common points of entrapment, and classic clinical signs and examination findings.

The median nerve supplies motor innervation to most of the forearm flexors and a few intrinsic hand muscles.  It supplies sensory innervation to the palmar surface of the thumb, index finger, middle finger, and part of the ring finger.  Compression of this nerve most commonly occurs in the wrist underneath the transverse carpal ligament.  The etiology is controversial but probably is caused by a combination of structural, genetic, and repetitive hand use factors.  Certain diseases such as hypothyroidism, acromegaly, amyloid, and diabetes can also lead to compression.  Symptoms of entrapment are mainly numbness, paresthesias, and pain.  Numbness and paresthesias are experienced in the sensory distribution of the nerve.  Generalized palmar numbness is not carpal tunnel syndrome, but may represent compression of the median nerve elsewhere.  Numbness usually occurs during sleep (due to a flexed wrist posture).  Pain may also occur in the nerve’s sensory distribution.  Weakness may be present, but almost always occurs following chronic entrapment.  Sensory changes always precede motor changes and are more sensitive for diagnosis.  Atrophy of the muscles between the thumb and index finger (thenar atrophy) may be present as well.

The ulnar nerve supplies motor innervation to one and a half forearm flexors and most of the intrinsic hand muscles.  It supplies sensory innervation to the palmar surface of part of the ring and entire pinky finger.  Compression of this nerve most commonly occurs in the elbow.  The ulnar nerve passes from the upper arm into the forearm just medial to the olecrenon of the ulna in the postcondylar groove.  It then passes between and under muscles to enter the forearm.  This is called the cubital tunnel.  The etiology of compression is usually trauma or arthritis in the elbow (tardy ulnar palsy).  Symptoms usually insidiously present as paresthesias in part of the ring and pinky fingers.  Weakness of the hand intrinsics may occur at the same time or even as the sole presenting finding.  With chronic compression, classic signs may develop such as Froment’s sign, Wartenberg’s sign, or hand clawing.  Hypothenar atrophy may also be present.

When entrapment is suspected, nerve conduction studies and electromyography are useful in validating the degree of injury and location, but clinical exam findings are the key to diagnosis.  The general distribution of clinical symptoms will identify which nerve (ie. ulnar, median, radial, etc.) is involved.  But the exact location of compression is more difficult to decipher.  Detailed testing of sensory deficits and key motor groups are crucial steps.  As branches exit off each main nerve at different points, isolative testing of individual muscles will determine, for example, if compression of the ulnar nerve is in the cubital tunnel of the elbow or Guyon’s canal in the wrist.  However, more common and classic examination maneuvers may be useful as well.  For both median and ulnar compression, tapping the wrist or elbow (Tinel’s sign) may reproduce the sensory complaints.  This is positive in ~60% of cases.  Using the contralateral extremity as a control helps to validate results.  For median nerve compression, flexing the wrists and opposing them (Phalen’s sign) may also reproduce the symptoms and is positive ~80% of the time.  For ulnar nerve compression, Froment’s sign may be seen by having the patient grasp a piece of paper between the thumb and index finger pads.  Pulling the paper will cause the patient to use the tip of the thumb instead, as the flexor pollicis longus substitutes for the weak adductor pollicis.  Wartenberg’s sign is characterized by an abducted pinky finger caused by weakness of the interosseous muscles.  Patients may complain that their pinky finger gets caught as they place their hands in their pockets.  A claw hand deformity may also be present.

Treatment of both carpal tunnel and cubital tunnel syndromes usually starts with conservative therapy.  Carpal tunnel syndrome commonly resolves with rest, NSAIDs, wrist splinting, and steroid injections.  Cubital tunnel syndrome is treated by avoiding any activities that exacerbate compression (such as repetitive extreme elbow flexion or resting the elbow on hard surfaces), protective elbow sleeves, splinting, and steroid injections.  Patients whose symptoms progress, despite conservative measures, and those who present with weakness, muscle atrophy, or significant denervation on nerve conduction studies should be considered for surgical treatment.

Carpal tunnel syndrome is surgically treated by making a small incision over the wrist and proximal palm and transecting the transverse carpal ligament.  This procedure may be performed using minimal sedation or a nerve block, and patients commonly go home the same day.  Cubital tunnel syndrome is a more involved procedure requiring the patient to undergo general anesthesia.  An incision is made over the medial elbow and the muscles and ligaments over the nerve are either decompressed or the nerve itself is transposed underneath forearm muscles to relieve compression.  Patients are still able to go home the same day.

For an evaluation or possible surgical treatment of peripheral nerve entrapment, please call The Neurosurgery Center of Colorado at 303-481-0035 to make an appointment with Dr. Adam P. Smith, MD.

Novalis TX is a linear accelerator utilizing high dose radiation to treat both intracranial and spine pathology.  Intracranial applications primarily include trigeminal neuralgia, tumors, craniopharyngiomas, hamartomas, epilepsy, and vascular malformations.  Spinal applications primarily include tumors and vascular malformations.

Like other stereotactic radiosurgical systems, Novalis TX offers a noninvasive way to treat pathology with ~1.5mm accuracy in an outpatient setting.  Unlike other systems such as Gamma Knife or Cyberknife, Novalis TX may have certain advantages.  Intracranial lesions can be treated using a stereotactic frame, or as a “frameless” procedure using a sophisticated image guidance system.  Additionally, extracranial applications exist, and the body may be treated circumferentially.  Probably the most unique attribute is the ability to treated lesions with a very conforming homogenous dose and sharp drop-off dose to surrounding tissue.  Numerous collimator options allow the radiation to be delivered in the traditional cylindrical fashion, or as a conformational beam, dynamic conformal arc, or IMRT.  This allows physicians to accurately treat non-spherical lesions with limited exposure outside the target.  Furthermore, the avoidance of purely cylindrical cones limits overlap of isocenters that produce “hot zones”, or non-uniform radiation doses within the target itself.

At the Medical Center of Aurora, we are thankful to have a Novalis TX on campus at the Rocky Mountain Cancer Center.  This technology is just another way our radiation oncologists, physicists, medical oncologists, and surgeons are able to provide the best cancer treatment to our patients.  Both Dr Adam Smith and John Oro are trained and certified in Novalis TX treatment.  Please contact our office today for more information at 303-481-0035.

Epilepsy Surgery

The surgical treatment of epilepsy is a valuable option for well-selected patients.  Patients who are not adequately treated with medications, who are proven to have a localized seizure focus, and who can accept the risks and consequences of surgery are candidates for surgery.  The most common location of seizure focus in adults is in the temporal lobe, where surgical removal is associated with a seizure-free rate of ~60-70%.  This patient population with temporal lobe epilepsy (TLE) has the greatest success rate from surgery.  A large study comparing surgery versus treatment with medications for TLE showed that 58% of the surgically treated patients were free of disabling seizures compared to 8% of the patients treated with medications alone.  However, treatment with medications is still first-line and surgery is reserved for intractable cases.  Most patients recover extremely well after surgery, including patients undergoing temporal lobectomy, with little disability attributable to the procedure.

Primary generalized (idiopathic) epilepsy is rarely aided by surgery, although vagal nerve stimulation (VNS) is an option.  Generalized epilepsy occurs when multiple different areas of the brain exhibit seizure activity, so no single area can be resected to decrease the seizures.  VNS involves placing an electrode around the vagal nerve, usually on the left side.  The theoretical mechanism of VNS is alteration of diffuse signals throughout the brain to suppress the generalized spread of seizure activity after it starts.

Other surgical treatments are tailor-made for specific problems.  Corpus callosotomy (CC) is used to stop the transmission of seizure activity from one side of the brain to the other.  Patients who suffer seizures that spread from one side to the other may suddenly fall to the ground during their seizure leading to a high risk for injury.  CC prevents this spread of seizure activity.  Hemispherectomy is a term used when the patient’s entire half of the brain is removed, or “disconnected” from the rest, when the entire side is dysfunctional due to widespread seizures.  Both CC and hemispherectomy are rare procedures used for very carefully selected patients.  Multiple subpial transection (MST) is another procedure that is used in carefully selected patients who have seizures that start in important areas of the brain that cannot otherwise be removed without causing extensive neurologic dysfunction.

New epilepsy research focuses on computer devices that are implantable.  These systems, such as Neuropace, use a computer to detect the very first signs of a seizure and then give a localized electric shock (similar to a cardiac defibrillator) to the part of the brain where the seizure is starting.  This then stops the seizure activity before it can spread to other areas of the brain.  Other implantable devices use a similar computer to detect the first signs of a seizure and then release an anti-seizure medication directly into the brain to disrupt the seizure activity.  These devices are still in early trials.

For a patient evaluation or possible surgical treatment of epilepsy, please call The Neurosurgery Center of Colorado at 303-481-0035 to make an appointment with Dr. Adam P. Smith, MD.